Hi, Excuse me butting in on this topic but I have exactly the same problem and have been following the steps above to see if I can find a resolution. I'm at the point where I'm running a Dr Web scan. The express scan showed no faults and the full scan is running as I type. - To while away the time while waiting for the scan results, I went back into regedit to try to change the "f" to an "S" again. While rumaging around I found that you need to change Permissions in the Edit menu before it will let you change the image path description. Not too sure how I did it unfortunately but I had a list of names in the group/user name list and two grayed out ticked boxes showing level of permission. - I did something that changed it to one name i.e. Base/ADministrator, ticked the boxes for access and then it let me make the change.
The bad news however is that it only let me do this in "BITS" and denied the change to Permissions in "Wauserv". I don't want to continue messing with these Permissions as I don't really know what I'm doing. - The answer to "unable to edit registry" that Filip was experiencing seems to be here. Boris.