Try uninstalling your display drivers in win7 then sweep it again with driver sweeper or driver cleaner . do a restart and install latest stable drivers of your device. since you mentioned overclocking i would suggest you to try running the gcard on stock settings. Run it on stock settings for a few days and if everything seems fine then try overclocking . also i would suggest to check the signal cable which connects the monitor to your gcard. ive seen a couple of cases where this wire was broken/loosened internally . try jiggling it a little and check for immediate colour changes. Hope this helps .