If you haven't checked out PortableApps.com, and you ever have to use a "strange" PC, you should  PortableApps lets you install some of your favorite freeware apps on a portable device (like a thumb drive) and run it on any Windows system from there.  You even get a nice "Start menu" if you install the Suite:

There are a few things in the suite that I don't use, and at least one that's not part of the suite that I do, so I still have a little cleanup to do.  Also, there are a few things I think I can add from my regular system like Reflector that should be "portable" already.

I've been using it fairly heavily over the last few days.  I have a second laptop that's borrowed from a client and I don't really want to install much on there, but this gives me my favorite apps.

The only caveat?  Not all flash drives and portable devices are created equal.  Some are quite slow.  Mine for example would be better called a flush drive than a flash drive, I think.  So, you may want to tweak your settings a bit to make them run faster.  The PortableFirefox page in particular has lots of suggestions on tweaking.

My other gripe is that the suite was released in November of 2006, and many apps have been updated since then, but not the suite.  So, if you want to use the suite, you'll need to install it (and the 1.0.1 patch), and then update any apps that are more recent than 20 November 2006.

UPDATE:  PortableApps also works great in my virtual machines, now that I've made the switch to VMWare.