I've just upgraded my desktop with SP2 after doing a clean install (formatted the hard drive first). It scr***d up Norton AV, so I tried to reinstall the whole SystemWorks Pro 2004. Tried several times, didn't work, so I went back to pre-SP2 version (thanks to N Ghost) and I'm back in business.
I waited a long time before reluctantly dowloading SP2, it seems that I was right to suspicious.