Many Antivirus will not install if a worm/other pest is on the machine. Do the usual scan with Housecall to see what you find.
Also, Symantec's AV is time limited. Yours may have expired.
I've been using SW 2003 for quite some time...maybe 2 years now. I originally had it on my desktop. I never had any problem reinstalling it after I would reinstall the OS ... XP Home. When I got my laptop I installed SW 2003 on it and upgraded to SW 2003 Pro for my desktop.
I probably installed the program on my laptop a couple of time after reinstalling the OS with no problems.
I just reinstalled the OS on my laptop and tried to reinstall SW 2003 but the antivirus wouldn't install. Thgere are things that just won't reinstall.
I haven't even installed any Windows updates yet and the OS that came with my laptop has only SP1. I've successfully reinstalled SW in the past but the only thing I can think of that is different is that the last time I reinstallled SW I registered it.
Anybody have a clue?