I assume that the CD worked under Windows XP, correct? Try to boot from a CD just to see if it still works in that mode. If it does, then it is a Vista vs hardware conflict.
I recently built a new computer using an Asus M2N Motherboard - Athlon 64 X2 3800+ - Nvidia 7900 GS PCI-E x16 - 1GB Ram - Western Digital Caviar SATA 250gb HD - and a Sony DVD-Rom. After installing XP then upgrading to Vista my CD-Rom doesn't respond to any CD's I insert. I've tried changing the IDE cables but nothing seems to fix it. Any advice would be great.