From Joel on Software I found out about VMWare which is software that lets you emulate several PCs running Windows 95/98/ME/2000K and/or Linux, FreeBSD etc. Check out this screenshot. There are both Windows and Linux versions. Each machine acts independantly so that for example you can configure one as a web server and another 2 or 3 as various clients and test out your net software on the same machine. Even better the software supports rollback (or hard drive undo) so you can install like Win2K once, test, click a button and have it get reset back like it was a fresh install. Pretty cool. I'd buy it except it's $300 and I don't have a $300 reason to own it at the moment.