If your serious about this, and don't mind spending a bit (or a lot) of money, invest in VMWare (
www.vmware.com). IMHO, it's WELL worth the $$$.
You can then set up lots of guest VMs (if you've got substantial RAM), using host-only networking, and have yourself a network on your PC.
As I type, I'm running Solaris 10, Fedora Core 4 and SUSE 9.3 Pro on a Windows XP host. And if I reboot (dual boot), I can do pretty much the same thing from a SUSE 9.3 host. I've assigned 256Mb RAM to each host, leaving 256Mb spare for the host itself. And it all runs very well indeed.
And the best thing about it is snapshots - if you screw things up, you can easily rollback.
Cheers
ZB