Something is seriously wrong with my computer...I have a Dell Dimension(2000, I think) that has worked very well for as long as I've had it. For about a week, the computer has been working very slowly. It takes a minute to load near every program on the computer, and is very slow restoring minimized windows. I also have to open IE twice before it will work without not "not responding." Sound like a virus? I don't think it has anything to do with ram, because I went through and took everything(except for like two or three things) off of the startup, and deleted most everything that wasn't absolutely necessary(Or that I really, really wanted...). Also, Norton Antivirus(Which is supposed to automaticcaly start up), will not open at all.
Go here and download the Klez removal tool. Follow the instructions and I think you'll find you have Klez.
If you are using a shareware program like kazaa then you might be having your bandwidth assualted from foreign computers and they might be using your ram along with numerous other computers to hack. Ask someone here like Ottomaton who seems to know about properly removing shareware products because I know that simply uninstalling them will not solve the problem. Many files put into shareware are designed to mark your ip address so that your ram can accessed and used. You will also find your pop ups rapidly increasing in number.