I was getting sick of having problems with all the PCs in our house not recognising that I had changed the disk in the CD/DVD Drive. It is a real pain when you are trying to do a multi disk install. Then with the help of google I stumbled across this.
http://www.naturalhandyman.com/iip/infcomputer/infrecognizeCDorDVDdisks.htmlThis is such a simple fix that I wonder why I never thought of it myself.

I thought I would share it in case other XP users are having trouble when changing disks.