I disassembled my hp pavilion dv2000 laptop for a cleaning of the heatsink/fan, which pretty much required removal of every component. Upon reassembly, the machine works better and is much quieter. The only thing is that the dvdrom isn't working properly. It has power and responds if I open the tray. If I put a disc in the drive, the disc spins up as it normally would, but the computer doesn't even recognize the existence of the drive! It's not showing up at all under device manager. Does anybody know what could cause this?