Just a guess, since I didn't test vrtool in Windows 8:
Try to run vrtool as administrator
( right-click program icon and select "run as administrator"
You have to be the computer administrator for that, or ask assistance of the IT guy )
You only have to run as administrator once, to have a few COM classes installed.
In theory, the program installer should do that for you, so that vrtool can be
used by regular users (non-admins)