Hello, you might be tempted to put your VMs to as much memory as you can spare. My testing shows it's useful to tune the VM to use as little RAM as possible when you know what you do with it. As I use my XP installation only to manage Active Directory at work, I have a blazingly fast Windows XP running with 128MB of RAM. YMMV however, if you plan using office or other, memory-hungry applications in your VM.
I completely agreed with oliof! Give VM as much memory as it really needs it to operation, not more. The more memory you left for Mac OS X the better overall system performance. I suggest 256M for guest XP - it is more than enought for most of the workloads.
