Access to CD/DVD Drive is Denied through Windows 7 Explorer (Permission Problem)

This behavior is very puzzling, so all I can offer are some hints and more questions.

It would help to know whether the CD/DVD drive is shared. If it is, maybe unsharing can help.

Second, whether you have a CD-burning software installed, such as Nero. You might try to uninstall such software to see if this makes a difference.

Third, run gpedit.msc and check Computer Configuration / Administrative Templates / System / Removable Storage Access. Verify that "CD and DVD: Deny read access" is disabled or not configured. In effect, all the options should be not configured.

You might also try to see what happens with "sfc /scannow" as described in
How to Repair Windows 7 System Files with System File Checker.

The last resort is following How to Do a Repair Install to Fix Windows 7, which will refresh your Windows files without requiring the reinstallation of applications.

Some anti-virus scans might also be useful.

Well, it turns out that I was right; it was indeed the missing Properties key in HKLM\SYSTEM\CurrentControlSet\Control\Class\{4D36E965-E325-11CE-BFC1-08002BE10318}. It took several steps to fix, but actually not that long overall (especially compared to the three or so weeks I’ve been living with and working around the problem).

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1. Grabbed a an offline copy of the SYSTEM hive from my previous installation of Windows-7 (the backup in %systemroot%\System32\Config\RegBack has the same problem)
2. Mounted it in my current copy (> reg load hku\z system)
3. Ran Regedit and navigated to HKU\z\SYSTEM\CurrentControlSet\Control\Class\{4D36E965-E325-11CE-BFC1-08002BE10318}
4. Opened the permissions dialog for the Properties key, ignoring the errors and warnings about not being allowed to view permissions for the key
5. Switched to Owner tab and set permission to myself
6. Switched to main tab and added myself to the ACL and assigned full-control
7. Refreshed and successfully viewed the Properties key and its contents
8. Exported the key to a .REG file
9. Unmounted the backup SYSTEM hive (> reg unload hku\z)
10. Edited the .REG file to change the key (HKEY_USERS\z -> HKEY_LOCAL_MACHINE)
11. Imported the updated .REG file
12. Navigated to HKLM\SYSTEM\CurrentControlSet\Control\Class\{4D36E965-E325-11CE-BFC1-08002BE10318} in the registry
13. Opened permissions dialog for Properties (no errors this time)
14. In Owners tab, switched owner from myself to the virtual user SYSTEM
15. In main tab, removed myself from permissions list and made sure SYSTEM has full access (iirc, it already did)
16. Refreshed, unable to view key anymore (that’s good), closed Regedit
17. Opened Device Manager
18. Uninstalled optical (CD/DVD) drives
19. Rebooted
20. Inserted a disc to test, observed that it loaded without suddenly turning into a hard-disk, opened the disc in Explorer successfully.

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It works correctly now (I can watch a DVD without having to rip it to the hard-drive or running the player in administrator mode, or I can install a game or program without having to open an admin command-prompt to install or even copy the whole disc to the HD).

I guess my instincts were correct from the start. If I had the time—um, at the time—I would have rolled up my sleeves and dug into that inaccessible key like I usually do. Thanks to harrymc for insisting on the key being accessible and pushing me to copy it.

(I’m still not sure what caused the problem in the first place. I do recall that there were other issues with the optical drives just before the key got deleted—Device Manager had kept marking them with an error/warning—and I recall trying various ways to forcibly uninstall the drives in an attempt to get Windows to detect and reinstall them correctly. It stands to reason that one of the forced uninstallations somehow managed to delete the key; it didn’t exactly improve the situation. On the bright side, the drives are no longer marked with warnings in Device Manager.)