Could be a simple case of a drive that has failed. Optical drives, burners in particular, fail pretty often. Anything over about a year of fairly regular use is just gravy.
It could also be that you've done something software wise, possibly even unintentionally, that is causing the problems.
A good test to see if it's hardware or software would be to download a Linux distribution you can boot off of a USB flash drive. Then try and burn a CD and DVD (both, since they use different lasers). If it works, you have a software problem, and if it fails, you need to replace the drive.
I'm running Windows XP Prof. v 5.1 - serv pak 3 (2007)
I have a DELL EXPERION w/a Samsung CD-ROM SC-148C internal DVD/CD-R drive (d) and an outboard Backpack DVD+-R/RW drive.
Until about a month ago I could burn and rip cd's as well as play & burn DVD's. I have both updated Real Player & WM Player on the computer. Haven't done anything radical to the computer that I know of.
I can still play CD's from the internal drive (d) but that's it.
Thanks for your help - CNET is a great resource for me.