His motherboard can only support 1GB max. luciusad, check to see how many memory slots you have. It might be worth your while to toss the old stick and get two new ones that max out your memory capacity, e.g., if you have two slots, take out your 128MB stick and get two new sticks of 512MB. Of course, it all depends on your budget. You could start with just adding 512MB for now and benchmarking it for about a week to see if you're satisfied or not.

In my personal experience, I've found Avast! to be an absolutely free, effective and low profile anti-virus program. Link. Many have also had good things to say about AVG. Personally, I can't tell you much about it.