All my games suddenly run slow

xzero1134

Distinguished
Sep 20, 2012
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So I have an unusual issue that I can't seem to solve.

First of all, my PC specs:
Windows 7 Home Premium
CPU: Gigabyte z87X-D3H
Processor: iCore i7-4770 @ 3.40GHz
RAM: 8GB
Power Source: Cosair 650Watt
Graphics Card: GeForce GTX670

So here\s the issue: I got a second graphic card to SLI to my main, same exact card. Once installed, games started running super slow, all of them, even old non-graphic demanding games. So I removed it and used just my on card again - but the issue persists. I have run Disk Cleanup, Defrag, Anti-Virus, Cleared my registry, drivers and DirectX are up to date, graphic card temp is at a 70C, turned everything off on startup with MSConfig, and STILL the issue persists. The weird part is I can restart my PC, it will run fine for about 30 min, then suddenly BOOM it just dramatically drops. I have no idea whats causing it. Cleaned out my PC it's dust free. Here's an image of the stats for my GC:
http://gpuz.techpowerup.com/14/11/24/9ru.png

Any ideas on what's going on and things I can try?