VMWare Server is free and it works like a charm. I run it on 64bit RHEL5, and have hosted 8 simultaneous VMs running all manner of OS - 'Doze, multiple flavors of linux, FreeBSD - without even breaking a sweat. The dual quad-core Xeon helps.... Seriously dude....my life has never been easier. If I fsck it up, I just delete the VM or revert to a prior good snapshot of it. Damn fast.