Yes. Thanks for that.
I think my point is, though, that users don't speak MS Registry. So for a non-savvy user, it's just as dangerous. And even for a savvy user, I'm not sure how many would recognise what all those GUIDs refer to.
The executable, too, came from winhelponline IIRC, but I can't check because the Windows box in question is currently choking at 99% done for the virus scan, scanning msvcp90.dll, which has been it's state for the last hour. But the scanning operation is still hogging the CPU.
(Edit: I checked. Yes it was from winhelponline. So the executable is just running the appropriate .reg files. The blog page with the link to the executable says: "Windows 7 & Vista do not provide a GUI option to unassociate file types, thus the need arises for such a tool...". What a crazy decision!)