Utility used for editing the MicrosoftWindows Registry. Not to be confused with ResEdit.
Someone at MicroSoft probably once said, "Nobody will ever need to use RegEdit to tweak a Registry system parameter".
(Wait. Doesn't your right to customer support get revoked when you *do* use RegEdit to stop Windows from screwing itself? (See Abandoned VbClassic GUIDs below)
Tweaking the Registry is the equivalent of going to the Unix /etc folder and editing one of the various files in there in its various file formats. Except infinitely longer, harder, and more annoying.
RegEdit is especially useful for manually cleaning up all the GUIDs VbClassic abandons.
-- A RegEdit junkie
For those who like a bit more automation, there is also the 'REG' command line utility. It allows you to export, merge and query the registry, and gives you an appropriate ERRORLEVEL back. This can be particularly useful when writing test scripts.
See also: ThingsWeHateAboutVbClassic, VbClassicIdeIssues