Drives

I have a cd-rom and a cdrw/dvd internal drives on my system. They used to work fine; audio, data, burned cd’s just great. Now neither of the drives are recogized in ‘my computer’ and device manager recogizes them but not the drivers states drivers are missing or corrupt. I’ve tried to reinstall the respective driver and firmware but to no avail. I have not been inside the machine for awhile, but the last time I was everything worked just fine. I’m running Win XP Pro on a Dell dimension 8100. Please help. Thanks all