VMWARE is NOT free,and virtualPC is VERY crappy. I can give you VMware if you want, its pretty simple to install too. All vm ware does is make a completely VIRTUAL computer inside your computer..such as a virtual cd drive. Inside vm ware you would create a "virtual" computer, after this you "power on" the computer and also make sure you have a virtual cd drive mounted with your Windows 7 ISO/Image file...then when your "powering on" your computer, just hit f2 of f12 just like you would in a real computer to get to the boot options..then you would select the virtual cd rom drive, it would boot up the windows 7 installation and youd install it on the "virtual" hard drive thats pre-built into vmware... and just go through the on screen instructions...formatting/etc etc. and vwala, you now have windows 7 on a virtual machine..
edit: windows 7 public beta wont be out for a while considering microsoft stated that w7 wont be released for another 3 years or so.