On some systems, PIO mode is so haneously slow that it can cause what you are experiencing. You may want to check your drives and CDROM to ensure they are operating in DMA mode. You find more information on this forum or the web if you do not know how to do this.
There could be a "bad" program running the background.. Perhaps some messed up software. You should open task manager and click on the "Performance" tab.. Check your CPU usage? Whild idling, it should be only a few percent or less.
How about your HDD light? Is it off.. Is it constantly on? This is a good indication of something chugging away at the HDD, which can cause simliar problems in conjunction with low memory. Perhaps a program is chewing up all of your memory and causing your computer to swap uncontrollably. Once again, check Task Manager and see how much free memory you have available.
Many things are possible, but I would probably check these out first. If you are using a PS/2 mouse, then try USB. If you are using USB, then try PS/2... Just some ideas.
As far as GTA3 being unplayable - Don't worry! - It isn't on most systems! LoL. Almost EVERYONE has problems with it.. It is simply a badly ported game. How do other games run?
Something else that can make XP unbearable to use is the absence of DX8 or better compatability.. Every time you click on a menu or drag a Window, it can pause and be painfully slow. If you buddy is using some half-assed, old drivers - Try the new ones. You should also install DirectX 9 with the new drivers, as that is what they are designed for.
