Dimension 2400 freezing after every boot.

Ok I have a big problem. On my other computer, Dell Dimension 2400 from about 2 and half years ago, everytime I boot it up and log into any account on it, it freezes within 10-20 seconds. I can still move the mouse cursor around fine but I can't click anything and nothing works, which forces me to reboot. Everytime I do it nothing works. I would do a system restore but I can't even get on to do that. What can I do? Right now I'm on my ancient Compaq. The thing is so bad that it revs up like a motorcycle if I even open two tabs on firefox =/.

Anyways I just need help. Any help would be greatly appreciated.

what about your keyboard , is it stop responding ?? seems windows loads your desktop. did you try with another mouse ??