256 MB of RAM used to be enough, but not after adding XP updates and pretective software such as AntiVirus and AntiSpyware. And certainly not enough if you have resource hogs such as AOL software for instance.
512 is really a minimum for a correctly working XP machine.
Of course an infection is still a possibilty, causing this issue, but more likely is just that you have too many programs running at once for the small amount of RAM installed on your computer. You can adjust the programs that autostart on your computer by following these instructions:Start > Run
" (without the quotes) Click OK
Click on the Startup
tab. Here you will find a list of programs that start when you boot your computer. Uncheck any you don't want to start when you boot up. (You still will be able to start programs through their shortcuts or by going to Start > All Programs
. Unchecked programs just won't start automatically at bootup and won't be running in the background.)
You can Google entries or use the Bleeping Computer Startup Database HERE
to research the various startup entries, as sometimes they can be a bit cryptic.