You lot seem like a clever bunch

I've whipped my DVD rom out of my old pc & put it in my new one, which is a 2400 athlon on an asus m/board, running xp home with an 80g hdd & a cd rom drive.
I've set the dvd rom to be the slave, with the cd rom as the master drive. The problem I have is that xp only very occasionally recognises that a dvd disc is in the drive - you have to repeatedly insert it for the system to eventually pick it up. It usually sees no disc at all. However, windows always recognises a cd rom placed in the drive, leading me to think that the issue is software based & not to do with my ability to plug stuff in. I've tried manually running dvd's in wmp to no avail & for the record, I run Cyberdrive power dvd 3.0, which I have updated with their xp compatibulty patch. Still have the issue.
I have just downloaded a patch from Microsoft (but haven't yet installed it) which talks about direct x 8.0 causing no playback issues on dvd roms, however, I'm farly sure the new pc is running dx 9.0 or above. Any ideas chaps?