I've been thinking for awhile about installing a virtual machine product. I want to read this article from the Altiris site to see what they say about the different products.
Based on my reading, Msft's Virtual PC is the easiest to set up on a Windows machine, esp if I'll be installing Windows XP. VMWare is the most capable, but the most complicated. Altiris' own software virtualization product works amazingly well for virtualizing individual application installs, but I think it's more for developers who can handle the abstractions than Joe Computeruser. (My comments about Altiris' SVS program are on this thread at Donationcoders.com.)