GPU clocks

[NeoFiren]

I tried to rev up my GPU clocks by using Riva Tuner. After cranking up the clocks by 200-300 Mhz, I tried to run a game. It crashed. I set the clocks to default and ran the game again. The performance was devastated! The FPS had decreased from 70 to 27...everything was very laggy. I restarted the system, but to no avail. I uninstalled the drivers and installed them again, still no luck.
Plz plz help me sorting this out. I don't want to lose my graphics card.
I'm using W7 64-bit.
And the clocks are perfectly normal.

[CAILYN]

You must first test your system stability before performnig any overclocking. It is therefore very risky for your system. Download and install OCCT. Run it for some hours and this software will tell you that whether your system is stable for performing overclocking or not. If the test performed by this tool fails then you have some fault in your system.

[NeoFiren]

Thank you very much for that. I will check my system everytime before OCing.
btw If anyone can still help me cope up with this current problem ,please suggest solutions.
Thanks.

[Hockson]

Have you tried downgrading the video driver for your graphic card, it seems that the driver might have got corrupted, use driver cleaner as well to remove all the remains of the video drivers. Check the temp of the gpu while gaming, whether it is too high or not. Reseat the card again from your computer, check something isnt burned or so, also clean all dust from it.