Remember kirky15, you will have the process mscorsvw.exe (.Net Runtime) recompiling the libraries for up to an hour after the install of SP1 and this can consume ~50% of your CPU. Plus for 64Bit it must do it for both 64 and 32.
A bit of an explanation here
http://blogs.msdn.com/b/davidnotario...27/412838.aspx
As for uninstalling SP1 try running this from an elevated cmd prompt (maybe in Safe-Mode).
"wusa.exe /uninstall /kb:976932" allthough if you`ve run disc clean up and removed the back up files i think your goosed!