well done, replacing Norton is one of the best things you can do for your computer
I use Antivir Personal Edition (www.free-av.com
) which is very fast, and light on resources. when running, I've never noticed a performance drop, even on my 500MHZ machine
what people don't often know of is spyware.
spyware is software that downloads itself, can give you popup ads (even when you're not online), take up resources, and even spy on your activities
I use Ad-Aware SE (free) and Spy Sweeper ($30)
Spy Sweeper takes up a fair amount of resources, so I only run it periodically, but it does a really good job at removing spyware.
Ad-Aware SE is free, and does a good job too. though not as good as Spy Sweeper
for defrag and disk checking, I just use Windows' defrag program and scandisk/chkdsk (chkdsk for 2000 and above) as they do a descent job