I have been having problems installing a program, and I suspect that registry keys left by a previous installation may be causing the issue. I have run CCleaner, and AMUST Registry Cleaner, but neither can remove these entries, and when I try to manually remove them, I receive the error message:- "Cannot delete - error while deleting key". How can I get rid of these seemingly 'locked' registry keys? I can't use safe mode, as my PC won't boot into it for some reason, but that's another issue.