updated the driver to the latest forceware AND (twas a mistake looking back) added manually the 2 keys. i added those 2 value after the pattern of another but existing colour-related values.
now it's fixed but i dont know what of the 2 different ways did so
XD
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btw if anybody will have the same problem in the future, and if it was the driver, i tell that i have a GF 6600 and had the driver installed from it's CD, but now updated to latest. so thats the possible fix.
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i will test to remove 2 two key and restart my pc, and if everything will be ok then we know that it was the driver. Thx for everybody's replies, and i will edit this post after had the test done.
EDIT1: omg its black again!!!
EDIT2: tests show that its only blackening now when i launch a full-screen direct3d application, or at least approximately this is the situation. Thias also suggests that its a driver-related bug.
EDIT3: 2 values removed from registry and still working (except as above) so it was driver 100% sure.