If you watch places like Fry's and NewEgg you'll find great rebate offers. Right now Fry's has the Norton AntiVirus for $9.99 after a $50 rebate (that link won't be good for long).

If you use a program like WinPatrol to keep track of the things that start up, and if you make sure that the stuff you're using isn't hogging the resources (I no longer run the "tea timer" in Spybot Search&Destroy - that was killing my processor speed) then you can have a secure computer and not too much inconvenience when it comes to the speed at which pages load.

SRS