my drives which have been working normally have now stopped and do not even show up on the computer. only drives a c and f. when i put a cd or dvd in the GREEN light comes on but after a few seconds just goes off WITHOUT loading. i am on windows 7 and as i said has been working fine.You could check devmgmt.msc (device manager) and see if the optical drive is listed there.1. Uninstall the drive through Device Manager.
Restart computer. The drive will be automatically reinstalled.
or...

2. DELETE Upper & Lower Filters
 HTTP://support.microsoft.com/kb/982116
Restart computer.
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3. Download, and run Restore Missing CD Drive patch
Double click on cdgone.zip to unzip it.
Right click on cdgone.reg, click Merge.
Accept REGISTRY merge.
Restart computer.
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4. Go to Device Manager, click a "+" sign next to IDE ATA/ATAPI Controllers.
You'll see two items:
- ATA Channel0 (or Primary Channel)
- ATA Channel1 (or Secondary Channel)
Right click on each of them, and click Uninstall. Confirm.
Restart Windows. They'll be automatically reinstalled.