Missing DVD/CD Rom drive letter

If your DVD/CDROM is not working ie..playing movies or not installing programs it may be becuase you have installed a ssoftware program that edited the regitry for the DVD/CDROM - (Limewire, any burning software, etc..) windwos installs an Upperfilter and or a Lowerfilter in the registry for the CDROM - to correct this follow these instructions:

To resolve this problem, remove the affected filter drivers.
To do this, follow these steps:
1. Click Start, type regedit in the Start Search box (Vista) or regedit in the Run box (XP), and then click Regedit in the
Programs list if in Vista or click Open in XP.
If you are prompted for an administrator password or confirmation, type your password, or click Continue. (Vista)
2. Locate, and then click the following registry subkeys: (must be exact keys)
HKEY_LOCAL_MACHINE
SYSTEM
CurrentControlSet
Control
Class
Once you have clciked Class the click Edit on the menu at the top
Copy and paste the following key inclcuding the curly braces into the Find What box.
Click "Find Next"
{4D36E965-E325-11CE-BFC1-08002BE10318}
3. Highlight by clicking on "UpperFilter" and "LowerFilter" ONLY - then hit Delete on the keyboard and select Yes
4. Shutdown and restart the computer