I don't think anyone has mentioned this, but if you're using VMware's fine virtualization products, then I recommend you use the free tool 'VMware Converter' to convert your physical, real Windows installation into a VMware compatible virtual Windows installation (retaining all your programs and settings in the process.)
You can learn more about 'VMware Converter' and download it here:http://www.vmware.com/products/converter/
Also, just some tips on virtual machines gleaned from my many years of using them (from way back to VMware 1.0)
1. Put your Virtual Machines on a separate Hard Disk or at the least, on a separate disk partition, so you can access them quickly in the event you re-install your primary Operating System.
2. Name your Virtual Machines with simple and consistent names so you can keep track of them (i.e., WinXP_Pro, Win98, SUSE10.3, etc.)
3. Store all elements of any single VM in its own folder (i.e., snapshots, disk images, etc...all in the same folder!) This make it easy to copy and past VM's to back them up or move them intact to other workstations!
4. Upgrade your system RAM! If you're going to run a Windows VM with any regularity, make sure your system has at least 1024 MB of RAM (2048 MB highly recommended!)
5. Whatever Microsoft recommends as a minimum amount of RAM, double it (or quadruple it in the case of Vista!)
6. If your processor supports hardware virtualization (known as VT on Intel processors and AMD-V (or Pacifica) for AMD processors) turn it on!! See the documentation for VMware (or whatever program you're planning to use) for instructions on how to enable it.
7. Once you have your VM's setup, you can safely delete any physical OS's unless you like dual booting.