Microsoft's TweakUI (for XP) renames the ShellNew key:
It works on Windows 7 too - but some patches or updates will change them back
If you play with this - and you rename it back to normal - then you might have to select the desktop and press F5 to refresh the context menu... or just restart the computer. If you ever do a repair of Office, they might come back too. One way to halt this is to make the keys read-only.
My guess is that there are several apps to pick from that will do this for you - I've just never gone hunting. I do it manually and I make them read-only. [Can you say "control freak"? :-]