On a side note, you may also want to remove BOINC from the HKLM run key: it places 2 entries there, no matter how you configure it not to run at start-up. What I mean is, even when you configure it (from its settings) not to run at start-up it does run at start-up, only it doesn’t start the distributed computations. Why this design? I have no idea…
PS: if you’re looking for HKLM run key: run ([windows key] + R) regedit then browse to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run. Then the values you want to smash are boincmgr and boinctray.

From what I read, there are many potential issues for switching from IDE to AHCI under Windows XP and Vista, and I can’t test those so I just won’t cover them. Basically on Windows XP you’ll need to install AHCI drivers, on Windows Vista you’ll need to apply the latest updates.

For Windows 7, the drivers are already there, but you need to activate them. That is, if you install Windows 7 on a drive already configured in AHCI, you have nothing to do, all will be handled automatically, but if your hard drive was configured in IDE when you installed Windows 7, then you’ll need to enable AHCI drivers manually. To do so:

• Launch regedit (hit start button, type “regedit” and hit enter)
• Navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\iaStorV key, and change the Start value from 3 to 0
• Do the same with key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci

That’s it, your Windows 7 is now ready to run on an AHCI drive. Now you just need to make the switch from IDE to AHCI in your BIOS.

Source: Microsoft Knowledge Base – Error message when you start a Windows 7 or Windows Vista-based computer after you change the SATA mode of the boot drive: “STOP 0x0000007B INACCESSABLE_BOOT_DEVICE”

If you’re still with me, on with the problem and its solution

The problem

When installing the latest Graphviz (graphviz-2.26.3.msi) on Windows 7 x64, I got blocked by the following error:

An error occurred during the installation of assembly 'Microsoft.VC80.CRT,type="win32",version="8.0.50727.42", publicKeyToken="1fc8b3b9a1e18e3b",processorArchitecture="amd64"'. Please refer to Help and Support for more information.

Some researched showed me that this can occur on various other Windows versions: Vista 32 bits, probably Windows XP (here’s a sure one), another one on an unspecified flavor of Windows 7, etc. So globally, it can happen with any “recent” Windows version, from XP to Vista.
From the look of it, I assumed this was once again an issue related to some Visual C++ Redistributable package, and after trying quite a few I eventually tracked it down to Microsoft Visual C++ 2005 SP1 Redistributable Package (x64 in my case). As a matter of fact, here is the original error from that Visual C++ 2005 Redistributable:

Error 1935.An error occurred during the installation of assembly 'Microsoft.VC80.CRT,type="win32",version="8.0.50727.42", publicKeyToken="1fc8b3b9a1e18e3b",processorArchitecture="amd64"'. Please refer to Help and Support for more information.

So here we are with that error and where it comes from.

The possible solutions

At first I tried the kind of thing that previously worked fine with the Windows SDK issue: I uninstalled almost all my Visual C++ Redistributable packages (I write “almost” because, strangely enough, the Catalyst Control Center was still up and working after I removed what I thought was the last one…). Then I ran the installer again: no success, even after a restart.

I then tried to look for solutions on Internet.
I found that weird one saying to install Visual C++ Express 2008… I didn’t even try it. In that same thread, which was for Vista, someone suggested to install SP1. I didn’t try updating my Windows either.

I also found a link to Microsoft’s knowledge base (sorry I lost it already) suggesting to repair/reinstall the .NET Framework 2.0. Well, I tried that, but the problem is that the installer will refuse to run on Windows 7 because the .NET Framework 2.0 is already included in Windows 7…

And finally, I found this, a bug reported SEVEN years ago and closed as “won’t fix” :s. The solution is simple: “It is a known issue when installing multiple interim releases. Go to %windir%\WinSxS and rename each *vc80* file to a different name. Then re-run setup.” Ok, that was posted by the time of Windows XP. Now in Windows Se7en, you can’t rename or move those files, even if you’re on an Administrator account. So we need… that other OS we mentioned at the beginning. I’m going to mention that disclaimer once again: messing with those system files can upset Windows and some of your programs. If you’re crazy brave enough, let’s continue
If your other OS happens to be some kind of Linux, you need first to mount your Windows partition (in Ubuntu just go to “Places” then pick the partition and voilà). Then open a terminal window, browse to the Windows partition (cd /media and then ls to find out the name of the Windows partition, then cd thenameyoufound). Once you’re in the root of your Windows partition:
cd Windows
sudo mkdir winsxsBAK
cd winsxs
sudo mv *vc80* ../winsxsBAK
Here we are: we moved all folders containing “vc80″ elsewhere. The strange thing with this is that, actually, when searching that winsxs folder on Windows, you see that it contains *vc80* files which can’t be seen nor moved from Linux. Never mind that though, moving what we moved is enough.
Now reboot on Windows. It may say something about applying updates or such, my guess is that it’s processing the changes we made to the winsxs folder. I then tried installing Graphviz again, and it still wasn’t working, but the error message was different (something about a missing dll or system file, I didn’t take a screenshot).
Now reboot (again) on Linux. We are going to… move back all those *vc80* folders. So, same as before, go to your Windows partition, then:
cd Windows/winsxsBAK
sudo mv *vc80* ../winsxs
Finally (this should be the last one now ), reboot on Windows. Once again, it will probably say something about applying updates or such. Try to install Graphviz again… hopefully it will work (it did for me!).

Oh, and did I mention the best part: the installer of Graphviz reinstalled precisely one of those Visual C++ 2005 Redistributable that I uninstalled earlier…

Update (2011-04-16): I forgot to mention that the Graphviz team is now aware of that issue, but the fix isn’t trivial with their current installer builder, thus the lack of a patched one yet.

• Open Windows Explorer (Windows key + E)
• Browse to C:\ProgramData\Microsoft\Windows\Start Menu\Programs
• You can then edit like in the good old days of Windows XP (add your new shortcuts or folders there, etc). Maybe you’ll need to claim ownership of the folder, but at least you’ll need admin rights to write there.

And voilà, you’re done. Now when you search the start menu you’ll find the links you just added.

Hint: my personal favorite is to place a shortcut to C:\ProgramData\Microsoft\Windows\Start Menu\Programs in the Quick Launch bar. Pretty neat trick, I can edit the start menu just as easily as in Windows XP now

What’s the Advanced Format Technology (AFT)?

To make a long story short, hard drives are organized into sectors. Each sector starts with a Sync/DAM block, then come the “real” data, then finally an Error Correction Code (ECC) block… and then a gap before the next sector (or rather, the next Sync/DAM block). For the last three decades, sectors have been 512 bytes big. This made sense when drive sizes were around some megabytes (since you can’t place 2 files inside 1 sector, the sector size determines the minimum space a file can use), but with today’s terabyte drives, this just doesn’t seem as appropriate (plus anyway modern file systems regroup sectors in indivisible 4KiB clusters). AFT simply changes the sector size to 4096 B (512 B x 8).
With this larger sector come the following advantages:

• for a 512 byte sector you needed 40 bytes of ECC, but for a 4096 bytes sector you can use only 100 bytes of ECC, a 220 bytes saving from what it takes for eight 512 bytes sectors (8×40-100=220).
• for a 4096 B sector you only need one Sync/DAM block, down from 8 blocks if you have 8 512 B blocks (although I couldn’t find anywhere if an AFT Sync/DAM block if bigger than a normal Sync/DAM block)
• each 4096 B sector, you get a sector gap, while on non-AFT hard drives you get a sector gap after each 512 B sector. So on AFT you have 8 times fewer sector gaps.

So globally, the main point of this is to stick more data into the same physical space (about 7-11% more according the sources I found – see at the end of this chapter – so the picture above is quite a bit exaggerated ). The use of one bigger ECC block instead of several smaller ones also improves burst error correction by 50% according to WD’s white paper on AFT. Finally AFT allows better performances (not a lot faster, but still faster): I didn’t find precisely why, but I guess this has to do with 8 times fewer sectors to read (since an AFT sector has 8 times more data) and smaller areas to read (since the AFT equivalent of 8 legacy 512 sectors is smaller).

I won’t go deeper into details, if you want further reading there you go:

• Western digital – Advanced Format Technology – White Paper (PDF)
• HotHardware – Exploring WD’s Advanced Format HD Technology
• AnandTech – Western Digital’s Advanced Format: The 4K Sector Transition Begins

What’s the problem with Advanced Format Technology?

As above-mentioned, 512 bytes sectors have been around for like an eternity. Thus any other sector size isn’t supported by, for instance Windows XP or even recent versions of Linux. To make the disk work anyway in all cases, Western Digital made it emulate 512 bytes sectors (see at the end of the white paper). So AFT disks will work in old OSes. But they won’t work in an optimal way: the OS will believe the sectors are 512 B, and thus will misalign clusters with physical sectors, which can be pretty much harmful for performance (although not at all physically damaging for the disk).

Ok, now what’s the solution?

If you’re on Windows or Mac OS 10.4+ using the GUID Partitioning Table scheme (GPT), check WD’s AFT page. If your Windows version is Vista or Seven, or if it’s XP and you’re sure you won’t need to edit any partition after using WD Align, that will be all.

Otherwise:

• if you’re on Windows XP and willing to edit your partitions after using WD Align, you’ll need either a third-party partitioning software, or Linux (I used Ubuntu 10.04 on this). This is because once you have aligned partitions using WD Align you shouldn’t EVER use Windows’s built-in partitioner (I tried that, it destroyed all my partitions in a fraction of a second) (note that you can still use Windows disk manager, just don’t try to modify the partitions with it on the whole AFT drive).
• if you’re on Linux: if you’re on kernel 2.6.34 you should be fine. Otherwise, if you have parted in its version >= 2.1 you can use it with the -a optimal parameter and it should create properly aligned partitions. The source of this information is WD’s Knowledge Base. They claim that Ubuntu 10.04 and Fedora 13 should align AFT drives properly (implicit: because they’re on kernel 2.6.34?). Well, Fedora 13 doesn’t, and has kernel 2.6.33 if I remember well, and neither does Ubuntu 10.04 (kernel 2.6.32). But Ubuntu 10.04 does have parted version 2.2.

OK, so, solved your problem yet? If not, I guess you’re either:

• On Mac OS using Apple Partition Manager (APM): you’re screwed, really. Yet, it works, after all… just not as fast as it could…
• On Windows XP, willing to edit the partitions later and not willing to buy a specific piece partitioning software: get Linux (you can just use some LiveUSB Linux: no installation required, can install/update packages if you configure persistent storage properly on your USB key)
• On Windows XP, willing to edit the partitions later and not willing to buy a specific piece partitioning software nor to get Linux. Well, you’ll have to make a choice: either don’t edit the partitions or get what it takes to edit them.

Or finally, you might be on Linux, without kernel 2.6.34 and not willing to use parted (or not having a recent enough parted), or just curious about aligning the partitions manually. Well, lucky you: I came up with a solution using GNU fdisk!

Update (17 August): here it is, finally, the fdisk + gparted guide: Dealing with WD Advanced Format hard drives on Linux (part 2).