Download Advanced system care, and avast anti virus (both free). Run ASC on a full scan, then open avast, go to scan for viruses, and set to "boot time scan" It will ask you if you want to restart the computer now, click yes, and leave it alone for about an hour! Most viruses will disguise themselves as part of the Windows operating system, and are hard to detect, but the boot time scan works before windows has started, and gets them all! See how many viruses you had and be afraid! Lastly use smart defrag in ASC toolbox to defragment your hard drive(s) Use ASC weekly and defrag and boot time scan on avast monthly. Dont use Macaffee, Norton, or any of that bought crap, they take over your computer, use masses of resources, are the very devil to uninstall, and believe it or not, are not very good either! I have the bought versions of Avast and ASC now, they are cheap and good, but you get full protection with the free versions, you get more scan and clean tools with the bought versions, and thye are both under £20 if you wait for the special offers. I have been running XP original install for about 7 years on my net access machine, with no problems whatsoever, .