Home Premium with SP1 beta.
Like quite a few people I had the Broken Start Button problem - it happened
after the PC lost power. Click the Start orb and nothing happens. It's fine
if you switch it to classic mode but does nothing in normal Vista mode.
CHKDSK and SFC (as suggested in an old post) didn't help so I was resigned
to living with classic mode as I couldn't be bothered run an upgrade/repair
then have to reactivate by phone.
But then I looked in the SFC log and noticed two files couldn't be
repaired - msshsq.dll and HotStartUserAgent.dll. I replaced them with
copies from a working system (had to boot from the DVD as they are "in-use")
and the Start Button now works again. Not sure which one is to blame ...