The speed of your processor has nothing to do with online security.

AOL is probably just trying to get you to upgrade to their newest craptastic release. Dump AOL, get a real ISP, don't use Internet Explorer, any email client with Outlook in the name, be sure to run an up to date anti-virus program, keep on top of all IE/Windows patches (even if you don't use IE), and avoid peer to peer programs and you should be pretty good to go with virtually any Windows version.