It seems to me that if you can't see any CD in this drive, that the drive may not be installed in the computer correctly. Is this a new drive that you purchased from us or somewhere else? Has the drive ever worked in this computer? There are some drivers for the Via Chipset motherboards that Plextor states can cause this problem on there website. Here is the link to there FAQ Page that explains this possible problem:
http://www.plextor.com/english/suppo...enabledma.html