Uninstall from program files? U mean from the Mozilla folder , the uninstall.exe, or U just tried to manually delete the mozilla folder and it won't let you?
Or did U tried from add/remove in control panel?
If you just deleted/try to delete the mozilla folder in program files, then U still have your profile left in the Aplication Data folder in your Documents and settings. It contains personal info such as bookmarks, cookies, etc.
U can get your bookmarks from there, if U don't need them, just delete the folder.(it's a hidden folder, just click Show hidden files and folders in any folder's Tools menu >Folder options, and U should see it )
And even if U mange to delete it, the registry keys remain.
if it gives you an error when U try to uninstall, what is the actual error?
I am asking this because some services might be in use (like plugin container) and U can stop it(them) with Task manager, then try uninstalling again.
Or U can try uninstalling it in safe mode (tap a few times, F8 at Windows startup and select safe mode)
Or if that doesn't work, we can try via cmd, later.