Computer Problem

[CYCLOPTERSAURUS]

my computer is running extremely slow. So slow in fact, that the mouse pointer lags, and the boot time takes nearly twice as long as my 450MHz HP computer, which is terribly slow. Since it involves the startup of the computer, I don't imagine it's any software thing, but I haven't a clue as to what it could be. I can't play games or anything as not only are the graphics shot, the frame rate is 1 frame every few seconds. The mouse still freezes up consistantly, and I don't have any idea what could be causing this. The slowdown starts at the windows loading screen, and it takes some 10 minutes to boot up from there.

Also, sometimes in the BIOS, it doesn't detect my Hard Drive, but upon reboot, it's fine. This is bizarre, because I had this problem several weeks ago with my secondary hard drive causing the problem and when I removed it, it was fine - I sent off for a new secondary HD, but now this starts up with my primary hard drive? I got the new HD and it works fine, and I haven't had the problem since, but I'm afraid it has something to do with my primary HD.