HELP NEEDED DESPERATELY…….. :(

Ok hello I would like to say that I have been working on this problem for months and months and haven’t been able to fix it so please be patient and help me as much as anyone can PLEASE.
I’m getting monitor flickering that turns black when on desktop or any white coloured screen i.e. internet explorer, outlook express etc.
I have tried re-install xp and alot of other things but first I would like to here your opinion about this.
System specs: AMD Athlon 1200, 256 RAM, Video card GeForce 2 MX 100/200