iMac graphics problems, or display problem, help please

hello everyone,
i posted this problem before and i was advised to update my graphics driver which i did but no good luck appeared.

anyway, my last post problem was not clear so i am doing it again with a clear images

these pictures describes my problem, on my iMac and running xp under boot camp i frequently get this grading issue

and this

also this


this happens like 2 times a week and wont go unless i restart my computer
these pictures are taken by my iPhone
if i do screenshot from the xp, the pictures are very clear and no grading issues when viewed by you, or even when i see them when i restart.

under mac, there no graphics problems at all.

i dont want to do a format, because i dont want install every piece of software again, and i have Tiger where boot camp expired

my iMac is alu 2.8 4GB and 2600xt

please help me solve this.
thanks.

yes 5 monitors
3 of them are name default monitor
one generic television
one plug and play monitor
sure i will post if i find it, i posted this in apple discussions see if i find a solution.