Sorry. I should have said. I'm running the exact reverse. Ubuntu Gutsy Gibbon as host, and others under that. Also a 512M RAM 1.6GHz P4. The guest OSes at 256Mbytes. I also use 8G dynamic virtual drives. I never tried using a fixed size one.
With XP running, my system slows up rather a lot, as it is using about 1.2Gbytes net RAM. I did at one point accidentally start a second virtual machine, but I killed it off quite quickly, as I couldn't see that being much of a success.
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"Striking up conversations with strangers is an autistic person's version of extreme sports."
Kamran Nazeer