My computer is ancient in computer age. When I put it together -custom mishmash- it scored in the top ten percent at PCPitstop; it now scores in the bottom 35 or less, except in one category.
It runs XP Professional (retail copy), SP3, AMD Athlon, 1.19 GHz, 768 MB RAM, 120 GB ST3120026A hard drive - Barracuda 7200.7, Maxtor One Touch II USB external hard drive 100 GB.
Security: Prevx, Online Armor Premium, Sandboxie, Trojan Remover, SpywareBlaster.
I uninstalled Eset's NOD32, got a partial refund, and bought license for Prevx. It is lighter on RAM use, 15 MB versus NOD32's 45 MB. Prevx is more effective too, and that says something. NOD32 is one of the best av products. So all of my real time security now has about the same RAM usage as NOD32 alone.