If you haven't done so, press the "menu" button on the monitor, and chose the "reset" option from the onscreen display menu. You might also need to check the brightness and contrast on the monitor itself, (under the OSD menu) - the manual for your monitor doesn't mention conclusively that the reset sets brightness and contrast back to default, although I'd like to believe that it would do so.
A greyish, washed out image is often the result of a GPU failure, and can be the result of a monitor failure, or (not very likely) a problem with the cable or connection. Do you have either another system you can check the monitor with, or another monitor you can check the system with?
As a last check, if you have a Linux Live CD/DVD handy (or if you don't, you can get one real quick from the internet) you could boot that and see if the problem persists. If it's still an issue on the Live CD, it's either monitor settings or a hardware failure with one of the two.
Is it possible that your "friend" also might have overclocked the GPU?
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