I had/have Norton Internet Security but uninstalled it while troubleshooting some game installation problems (FIFA 2004 - see below).
It was a 3 year old 90 day free trial that I didn't upgrade. Seemed to spot Trojans and attempts to penetrate my system (at least it told me so) but I perceived that it slowed everything down to shit.
What are the alternatives? Cheaper the better.
Installed FIFA 2004 on my Dell 1.7GHz P4 with Xp SP2. The fucking thing REBOOTED my PC whenever I tried to run it. Never in 3 years of using this machine did a game ever cause this hassle. Got new Geforce 3 Ti200 drivers from Dell site. No luck. Then Windows error analysis told me it was still my graphics drivers, so downloaded newer drivers from MS update site (thanks a lot, Dell). That fixed the problem. Sound wasn't working then (even through DXDIAG was fine), so got drivers from Dell again - still didn't work. Got newest drivers from Turtle Beach site (thanks a lot, Dell, again) and still didn't work. Finally switched off hardware acceleration on sound and now can hear most stuff.
FIFA200 is the worst programmed piece of shit ever.