Darren J has an excellent blog entry on how he was able to install Visual Studio 2005 Team System Beta 1 Refresh onto a single PC using Virtual PC. The most telling line was the last, however:

If you haven’t got 2GB ram on your laptop and your running this on VPCs, you best get an upgrade.

Uh oh. I'm going to do the install this afternoon. I might need to run out to Best Buy really quick!