What Killer? - What exactly does it kill, again?

The batch registry edits were originally designed and tested only for Windows XP. Vista and 7 probably use different keys and may even be different from each other.
You'll have to do some searching around for the equivalent under Vista 64bit.

Thanks for the tip. I looked around and found this other key:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{a2a9545d-a0c2-42b4-9708-a0b2badd77c8}

When this key is deleted from the registry under Vista (possibly under 7 too), the start menu doesn't show up anymore!

So I am partially happy, although if I really wanted to be pedantic, I would love for my replacement button to "claim" those few pixels around as well, like the official start menu does (and with reason, since we are rarely precise with a movement we do tens of times a day). Unfortunately using a larger custom image for the button doesn't do it, those few pixels in the corner are still left uncovered.