Need help diagnosing the lag!

I can't stand it anymore, sometimes i have no lag at all (which is like 15% of the time) and 85% of the time im pure lag. I use game booster, RAM cleaning softwares, scanned my pc, upgraded all my drivers, used heaps of programs, updated my windows, cleaned my disk, defragmented my hard driver and put the lowest possible visual settings. I don't know why but i still lag so bad.

My computers specs are

450GB HDD
4GB RAM
TOSHIBA SATELLITE
ATI READEON HD MOBILITY HD 3650
290GB FREE


WTF am i doing wrong? All games run good exept CA. I tried it on my brothers comp (2gb ram, very low disk space and old computer and it works really good)

I also tried using the No gun hack and it seemed to reduce the lag alittle. I think it is my mouse, im not sure. Suggestions? Help?

P.S I have a laptop and have tried disabling the touchpad, too.

reply plz