Cannot delete windows.old (Even with diskcleanup or cmd.exe)

I was stupid and manually tried to delete windows.old. Didn't work. So then I decided to see how to properly do it. Well apparently by manually trying to delete the files, when I tried to use diskcleanup and look for the "Previous Windows Installation" check box does not show up anywhere. I assume its because I'm an idiot and tried to delete windows.old myself manually. Hmph!!! After all that I tried doing the cmd.exe method. It ran but all files said, "Access Denied". So am I completely screwed? Do I need to completely reinstall windows now to fix this or is there some way to do this still? It takes up about 27 gigs of space so I would really like to free that up. Thank you for any advice.

As long as everything is working fine, you don't need to worry about this. In fact, you can safely delete the contents of WINDOWS.OLD.

You can manually go through the various subfolders of WINDOWS.OLD, one at a time, and delete most of the contents of these folders. You can likely delete most of the subfolders as well. Once you have done all of that, there won't be much left under WINDOWS.OLD.

In the past, I have found that if I reboot into Safe Mode, I can delete all of the contents of these types of folders. I'm not sure that you have to go into Safe Mode to do this, but that is what has worked for me.

The only problem you will have from doing this is that you won't be able to go back to a previous install of Windows. That is what was in the WINDOWS.OLD folder.