Sysprep, Virtual PC's best friend
I discovered Sysprep recently while discussing with some Virtual PC product team members at the MVP Summit. Basically I wanted to install and set one XP virtual machine and use it multiple times. The problem is when you need to run two virtual machines at the same time; they have the same name.
Once you have created, installed, configured to your heart one virtual machine, you run Sysprep to "reseal" the image. The next time you run the virtual machine, it will ask for the product key, machine name and network info but all the apps that you installed before running Sysprep will still be installed. Cool !
Sysprep.exe can be found on the XP CD in the \Support\Tools\Deploy.cab file. You also need to extract Setupcl.exe.