Reinstalling Vista

I have a custom built PC with an OEM vista home premium. After having it run
vista for over a year, it has start to slow down alot. Cleaning out the
registry, defraging and cleanign the hard drive does nothing so im assuming a
fresh vista install will sort it all out. Thing is, will my product key still
work as ive heard numerous stories of people being froced to purchase new
keys due to vista not recognising their hardware. Furthermore, i have a 1
license version of office 2007 ultimate which was being given away at an
extremely low price as a deal with microsoft. Will my office key still work.
I have done clean installs on my old xp computer before no problem but now
microsoft has introduced strict rules on product keys etc, im not sure
weather its worth the risk on my vista PC. Anyone got any advice?

Thanks in advance