Microsoft Virtual PC 2004 45-day Free Trial Edition

Do you have this system requirements?

Processor: Athlon®, Duron®, Celeron®, Pentium® II, Pentium III, or Pentium 4
Processor speed: 400 MHz minimum (1 GHz recommended)
RAM: (depending on how many GuestOS would you run)
Available disk space: (depending on how many GuestOS would you run)
Other: Level-2 cache and CD-ROM required
Operating System: Windows 2000 Professional, Windows XP Professional, and Windows XP Tablet PC Edition

Then you can download here and try from yourself how good Microsoft virtualization technology is.
Consider also reading the evaluation guide.