There is a known issue with 2003 - and probably 2004 as well - that causes a Norton subroutine known as REGFILTER.EXE to run wild and eat up your CPU use. The computer runs very slowly, and none of the Norton programs will start. REGFILTER is part of Norton Personal Firewall. It's more likely to happen if you have Norton Antivirus 2004 running under System Works 2003...which they say is fine.
I beg to differ!
My suggestion - buy a McAfee Internet Securities Suite V7.0 for $39.95 at K-Mart and ditch Norton. They're simply not what they used to be.