sp3 is has never been a problem for me
but in the past problems have always been due to drivers
I've tried to make a slipstreamed disk - but for some reason it won't accept a corporate serial number ...
see
http://www.nliteos.com/download.html
so I always start with a slipstreamed sp2 install
I also always update mobo and video drivers before applying SP3
(I always use the full service pack file - not the updater)
Cheeky - consider slipstreaming to sp2- it will cut the updates to less than 20