How to install Flash Player on Firefox Portable or Opera-USB

UPDATE because quite a few people still seem to land on this page: a current portable version of Flash is available in the Flash category (usually it’s the top post, sometimes it might be a little bit below). The XPI is only presented for illustration purpose, it’s totally outdated otherwise!

For a shorter/faster version lacking details, see the Quick Guide at the bottom of this post.

Firefox Portable, published by PortableApps.com, is a version of Firefox specially designed to be run from the folder where it is, without requiring an installation. This means that it can be used without administrative privileges and from a removable media like a USB key. So in More tips to freedom on a restricted computer environment I presented it as the way to install Firefox on a restricted computer. Opera-USB is the equivalent thing for Opera (except that since Opera isn’t free software it wasn’t made portable by PortableApps).
Leaving aside the connection configuration issues that were dealt with in the above-mentioned post, there is another problem with restricted computers: you can’t install plugins like Flash or Java. I didn’t study the Java case yet. But as for Flash, Firefox will use the installed Flash player if: 1. there is one and 2. the one installed is the generic version (i.e., multibrowser) and not the MSIE-only version. Which means that on a classic restricted computer happily limited to MSIE 6, Firefox Portable will most likely not be able to use the installed Flash player.
I found 2 ways to solve this problem:

Solution 1: the XPI

Adobe published a special version for Firefox, which is supposed to install like any other extension (aka now add-on). It turns out that the XPI fails to install. But, you can download it manually (for this you’ll need to right-click the following link and choose “save as”: http://fpdownload.adobe.com/get/flashplayer/xpi/current/flashplayer-win.xpi), unpack it (with any archiver supporting zip, i.e. you can do it with Windows if you change the file extension from .xpi to .zip), grab flashplayer.xpt and NPSWF32.dll and place them into the plug-in folder of Firefox Portable (in Data/plugins). Restart Firefox and voilà. For Opera-USB, the plug-in folder is program/plugins.
This method works and is quick and easy. The only problem is: Adobe doesn’t seem to update their XPI as often as they update the executable installer. This results in an outdated and thus insecure plug-in. As I’m writing, the version of the XPI is 10.0.32.18 (17 July 2009) while the current version is 10.0.45.2.

Solution 2: hacking the exe

Thanks to an article on eHow, I found this promising software called Universal Extractor (NB: it exists in a portable version). This free program, released under the GNU GPL v2, was designed to extract files from any type of archive or installer. It was suggested on eHow to use it to manually unpack the Flash installer, then grab the files as mentioned above about the XPI. Thus I downloaded the generic installer here (direct link), but when I tried to extract it with Universal Extractor it failed. I tried my luck with a 10.1 release candidate (RC4) from Adobe Labs, but it was not much better (it succeeding in extracting the files, but they all had strange names thus I couldn’t find the proper files, plus I thought they might be damaged anyway).
So, this leaves me with only two choices: grab the files from my home installation or grab the files from a site I consider safe to trust. For now I chose the second option. I came across a blog hosted by Opera Community, Tamil. They posted an up-to-date version of NPSWF32.dll. For Opera-USB, this is enough. For Firefox Portable, use this file along with flashplayer.xpt from the XPI. Restart your browser, then check your Flash installation.

Edit: at my home Flash installation, the Flash files (version 10.0.45.2) from my Opera plugins folder have the following MD5 checksums:
NPSWF32.dll: f8efdcfc440a420d6c1ecd245ab20207 (size: 3884312 bytes)
flashplayer.xpt: a81fd3b03b8c6d6e5a14298110718d3f (size: 856 bytes)
I compared NPSWF32.dll’s checksum to the one at Tamil’s, it’s the same.

Sources and versions

While dealing with this $#!t I found the following more or less useful pages

• Install Flash Plugin Manually in Firefox on Vista on How-To Geek
• How to Install Flash Player on Firefox Portable on eHow.com
• Flash version checker on Adobe.com: I already posted about it, but it’s so useful that it never hurts to remind it sometimes.
• Tamil – How to install flash player without administrator privilege for Opera?
• Hash functions on FileFormat.info: this page lets you calculate the most common checksums for a string or a file (md2, md4, md5, sha1, sha256, sha512…)

I did those things to Firefox Portable 3.6.3 and Opera@USB 10.53 on Windows XP SP2. The Flash versions I tried were 10.0.32.18, 10.0.45.2 and 10.1rc4. No registry key was hurt in the process, no CPU burnt and no hard drive failed despite the massive use of swap due to the ludicrous 512 MiB of installed RAM.

Quick guide (updated for Flash 11.1)

1. download NPSWF32.dll and flashplayer.xpt
2. save those files in Data/plugins (Firefox) or program/plugins (Opera)
3. restart your browser, and optionally check your installation.

Update (June 1): you can also grab Flash 10.1 RC6 there.
Update (June 12): you can grab Flash 10.1 final here.
Update (22 March 2012): replaced broken MU link by a MediaFire link to version 11.1.