I think the fast speeds are the results of using AOL. They proxy everything, or at least they did in the past, so the speed is of the AOL proxy servers not your connection. Try using IE directly instead of the AOL web browser.
Hi,
It sounds like maybe a hardware issue. Perhaps bad memory or your CPU fan went out.
You may also want to try running the following command (start>run) to be sure your XP system files are intact 'sfc /scannow'.
~Brian