The registry is corrupted.
http://support.microsoft.com/kb/982116
there is a registry editor that you can try to fix the problem.
I recommend you do not use third party downloads to try and fix this.
There is also another way,
windows 7 can be reloaded without erasing your files and programs.
this also corrects problems...
set the bios to boot the DVD drive first.
turn off all security antivirus and firewalls.
put the win 7 disk in the drive and start the computer
select upgrade
The upgrade will reconfigure everything, and clean up what's goofy.
After it runs restart and turn the security back on.
The drive should work again.
However certain updates may be corrupting the registry and causing the problem.
Therefore if updates are turned on, the same problem may reoccur.
You might want 'critical updates only' or to update manually.
OR check with the manufacturer(s) for a list of incompatible updates.