I expect that the answer it "Yes," but did you run Disk Cleanup "As administrator" and not just from a user account with "administrator" privileges?
Take a look in the following locations:
- I believe that the System Queued Windows Error Reporting Files are here: %ALLUSERSPROFILE%\Microsoft\Windows\WER\ReportQueue
- But they might be here: %USERPROFILE%\AppData\Local\Microsoft\Windows\WER\ReportQueue
On the system I'm looking at, the above folders, which happen to be empty, are in blue text, which means that any files in them are supposed to be compressed.
If you find your 12GB of files and have difficulty manually deleting them, it's likely to be a permissions problem. Right-click on a file and select Properties, then take a look at the "Security" tab.
Be careful when making changes here. These system files/folders have some fairly esoteric permissions and properties, but the "Administrators" group should have "Full Control" permission, which means that a member of the Administrators group should be able to delete them.
If you have a problem other than permissions, post back with the complete text of the error message.