VirtualBox is available for Windows, OS X, Solaris and is also pre-packaged for all major Linux distributions. 2.1.4 is a maintenance release, fixing a large number of issues on all hosts. No reason not to upgrade :)
FWIW, I recently installed Office 2007 (need it at work, yuck) on my Windows XP image. Runs just fine. No crash, no slowdown. Isn't it funny that Windows works better with virtualization software than natively?