Check for UPPERFILTERS and LOWERFILTERS in the registry: http://support.microsoft.com/kb/314060 and correct it if necessary.
If that doesn't work: do a system restore back to when it still worked.
If that doesn't work either: try if you can still boot from a bootable CD. If that works, it's a Windows problem. If that doesn't work either it's a hardware problem. Looking at those drives in the BIOS is good intermediate step.
Please post your findings.
I started my computer and all of a sudden it will not recognize my cd & dvd drives. It was working fine the last time I used it. I have a pc with windows xp. Any suggestions. Thanks