I'm a Mac newbie who usually uses PC's. I installed VPC 6 today to run a couple of my must-have PC apps. Everything went smoothly but I've got a question. The install prompted me to designate the amount of RAM you're willing to allocate to VPC. My questions is, is this RAM allocated only when you're running a VPC session, i.e, when Windows is running? Is the RAM released when you shut down VPC? I don't want my OS X peformance to be gutted when I'm running VPC. I've got a TiBook 1ghz w/ 512mb. I've considered upgrading the RAM, but my understanding is that adding RAM to this thing means tossing one or both of the existing 256mb modules in favor of one or two 512mb chips. Is this right? Thanks for any help.