Oops.
Otherwise, I run Virtual PC on this Mac here, as well as VMWare ESX Server and other programs.
Virtual PC is OK, and it lets me run multiple OSes at once (I use it to run Linux and OpenBSD on my Mac for network utilities OS X doesn't have yet).
VMWare has much better Linux and BSD support
.
Otherwise, both run by emulating a complete machine in one main process, with VMWare utilizing several device drivers to improve performance. Virtual PC does the same on OS X (which is why you can't run it on the Intel Macs just yet, it utilizes kernel extensions). I don't know how it does kernel-level extensions on Windows.
My apologies for getting this one a little wrong
.
Mitch