I have worked with Office 2010 x64 for a while now but because of compatibility issues I wanted to remove it and install the x86 version instead.

After uninstall Office left a key in the registry:


I couldn’t remove it so I figured there was a specific process that had opened this key but couldn’t find anything (using Process Explorer).

Then I checked the permissions on the Office key but it was set to Full Control for Administrators.

Then I checked the {B7EFF951-E52F-45CC-9EF7-57124F2177CC} subkey and under the special permissions the Delete permission was missing:


So I reset the permissions and then I could remove the key: