yeah, I use norton corporate edition. uses much less resources. and at home I use norton system works 2002.
and I have never had an issue w/ norton fucking up, or slowin my shit down etc... I guess it kinda matters how you have it set to scan. if you have it scanning every single damn file yeah it might get slow, that's why I have mine set to only scan incoming emails, and exe,com type files.
Also my computers I use at home and work are dual 1.4GHz, w/ 1GB DDR ram, and nvidia Ti4600 w/ 256MB DDR on them as well.