Memory issues on PC

Greetings:

I’m having memory issues on my PC. Things to note: I recently added 256mb, with a pre-existing 64mb for a total of 320 mb. I also recently had the Goner worm which is now innoculated/removed from my system. I’m getting lots of messages related to shortages of memory and the system is behaving as though there isn’t much memory at all even though it shows that there are 320mb. I have the Fixit 99 utilities and I ran the system through the diagnostics and all the memory tests worked out fine. Does anybody know what kinds of things I should be looking to do?

THANKS SO MUCH!!!