I am trying to install windows xp pro on a pc already running windows xp media center edition. I am trying to do a clean instal (format hd etc) and when I boot from the CD and get to the screen about where to install it, there are no drive letters listed and I get an "Uknown Disk" message followed by message "There is no disk in this drive". I don't have any partions setup - just a plain old C: drive. What is the issue? I would format it, but not sure what all that would do to a potential reinstall of the OS