personally, zone alarm & AVG, as both are free and AVG takes up little resources compared to the likes of norton. but, thats just my opinion
ZoneAlarm & Nod32 are the very best your gonna get
If you attack the establishment long enough and hard enough, they will make you a member of it.
-- Art Buchwald --
For simple and little interferance I say Sygate and AVG which is what Ive always setup for others on their pc and dont forget CCleaner and a decent Spyware AdWawre app like AdWare although there are other choices for AV wgich may be better although I havent used them although I really must say I think after using it quite a bit ZA is shit since especially for a file sharing type pc setup...
get sygate as it uses very small system resources and grab Nod32 , @ Reality i dont use avg anymore as since the upgrade to the new free vesion its gotten pretty clogged up and does use a far amount of your system resources now
Open your mind
sygate/zonealarm and nod32 (hopefully that works in 98!).
Well hell... if you just utilize eMule/eDonkey, some of the more premium set-ups (i.e. Symantec Client Security... izzy's personal pick ) can be "free" also.