Should be. If he doesn't, it probably means he didn't do it the
right way.
By the way, the registry corrupted, that's why it caused the above
symptoms. Either he reset everything manually (trust me, you will
cry, there are thousands of extensions in Windows) or the best way
is just to reformat.
There's also a registry fix for fixing the extensions problem, but
it's only a few lines. Can't really tell if it's useful.
