To be honest I think it's one of the occaisions when it's best to seek trusted professional help to ensure that all the possible back-door techniques have definitely been expunged. I had to do the same a few years back when my late mother fell for just such a scammer, and the specialist showed me the nine different "hooks" that the scammer had installed. The chap I used is a local whose main business is providing IT support to tiny companies - he's just over the valley from me. If you don't have anyone local that you know about I guess you might be quite close (Berkshire's border isn't that far from me), so if you want his details drop me a PM.