Virtual Machine Issues

I would imagine one of the big issues with Virtual PCs in Microsoft shops is licensing. Unless you have some special licensing, I believe you have to have a license for each copy of the operating system you have installed, as well as any other Microsoft software you have installed on each machine. The next issue would be trying to track this. Tracking software inventory of physical machines is enough work, let alone having virtual machines. If you are using a software tool to track your software inventory, then you may have to figure out the licensing of your inventory product. Is it per user, per physical machine, per OS, etc..