I have XP in a Boot Camp installed, and Ubuntu in a standard install. They're both 512mb virtual machines; when I got my MBP, I had 1gb RAM total, and I once tried running both the XP and Ubuntu sessions simultaneously (on an earlier beta). It was disastrous; slowed the machine to a crawl so I couldn't even use the mouse or keyboard to kill the processes, and I had to hard-reboot, which destroyed my boot camp partition and everything on it. Luckily I was just experimenting, so I didn't lose anything important, and I'm sure it was at least partially due to the fact that my VMs' total memory allocation was more than my physical RAM, so I was in swap hell. I've since added a gig, for 2g total, and I'm wondering if anybody ever runs both a Windows and a Linux (ubuntu/etc) session at the same time, switching between them, or whether that's verboten? I do actually have a need to do this. Will enough RAM make this possible, or is Parallels really a one-at-a-time VM system? Thanks for any tips.