ok, I found it under local, but no screen entries. One file folder (called morrowind ofc) has two items in it. both deal with the path of the game. I can't edit screen res or size. In fact when I click on it, the only value I can edit is its name and installed path.
You might have to manually add them if they weren't created/initialized.
Go back into:
HKEY_LOCAL_MACHINE\Software\Bethesda Softworks\Morrowind
in the right panel, right-click and select New DWORD (32-bit) value. Make one
Screen Height and another
Screen Width. Again make sure you save the value in Decimal (not Hexadecimal) or enter the correct value listed below.
Screen Width is 1024 (decimal) or 400 (hexadecimal)
Screen Height is 600 (decimal) or 258 (hexadecimal)
edit: oops... screwed up width and height... fixed