How to remove the WDAG utility account..

This account CAN be removed completely. Though if you want to use wdag or sandbox you should not remove the wdag account because it is needed for those functions.

Open regedit, take ownership of the following key: HKEY_LOCAL_MACHINE\SAM (also subkeys).

move to HKEY_LOCAL_MACHINE\SAM\SAM\Domains\Account\Users\Names. Note the wdagutility account and the default value it has. Delete this wdagutilityaccount key.
then move to HKEY_LOCAL_MACHINE\SAM\SAM\Domains\Account\Users\ and look for the key with value you just noted in wdagutility account (000001F8 most likely) and delete that key too.

After this you can replace ownership of the SAM key and subkeys back to the original owner .

Reboot and now your wdag utility account has been removed, and can not be added again without a clean install again.

Why do I need to remove this WDAG account? In other words, what do I GAIN by deleteting it.

And why would I need to 'use' it... or what service normally uses it and what for? In other words: what do I LOSE by deleting it.

This utility will do it without touching the registry but as the previous post rightly asks: what is the point?
Useful to those on the Home version of Windows.