[dba-SQLServer] SQL install f**ked up

I have asked this before in several lists but so far received no useful
response, so I'll try again. Can anyone provide a recipe that is
guaranteed to blow away all traces of MS-SQL on my development machine?

Everything used to work fine, by which I mean the server, EM, QA, Yukon
beta, etc. Then something happened, no idea what, and now nothing works.
I can't uninstall successfully, I can't re-install... Nada! I even
booted safe and renamed the directory, then reinstalled and even that
didn't work.

Fortunately I have other boxes that I can use, and of course all the
data is backed up safely (and now resides on said server), but that's
not the issue. I want to blow away every trace of SQL on this box and
then successfully re-install. Any suggestions, short of a complete
reformat?

TIA,
Arthur