Computer locks up at random times

my computer is also locking up at random times. HELP! it seems to not matter, i can be just chatting or streaming media or playing a game..no real rhyme or reason to it..just locks up..to the point i have no mouse control and cant do ctrl alt del because it won't work, the keyboard is locked as well. I am running XP and I did not have this problem until I was forced to install SP 2 because of my wireless network card..I have a feeling it has to do with either SP 2 or something to do w/ Active X ..I think I may be missing some .DLL's but im not sure?