Yeah, that's not the problem. It's getting the VMs themselves. I mean, I know you just load up the software and start up a virtual machine, then load your OS on it. VMWare won't let you do that free, tho. Maybe I should look at Qemu or something else.
Got the link to the demo version of windows XP or windows Vista?
VMware server is free and lets you create empty VMs and install software on them, as do Virtual PC and Sun XM VirtualBox.
I would avoid VMware Player, which may be what you are thinking of. It's pretty limited.
The downside to VMware Server is that it loads a bunch of support stuff on your PC that can degrade performance if you aren't using the VMs often or for anything complicated.
I like XM VirtualBox, but if you are doing Windows OSes only, I would consider VirtualPC. It's a pretty weaksauce application for anything fancy (32-bit only, ugh), but it's as easy as pie to use and has great Windows support (and also doesn't load up anything when you aren't using it, which is also true of VirtualBox). So yeah, either of those two should suit you fine.