Strange Graphics Card Issue

I have an Nvidia GTX 560 Ti. Lately whenever i boot up my computer, the graphics card has extremely low performance, not even letting me launch most 3D games. The performance is so terrible that it is almost unusable for any type of gaming. The first time this happened I downloaded and installed the newest Nvidia drivers which seemed to fix the issue. However upon restarting the computer was having the same issue. What is strange however is, though the latest drivers are installed, if i Re-install them the problem goes away again until the computer is restarted. I'm pretty sure the drivers installed properly because the Nvidia scanner recognizes that i have all the latest drivers installed. Though reinstalling the drivers every time I start the computer works it is getting a bit annoying and is a waste of time and I'm wondering if anyone can help with a more permanent solution, Thanks!

Specs:
Motherboard: Asus P8Z68 DELUXE/GEN3
Video Card: Nvidia GeForce GTX 560 Ti
RAM: 8Gb DDR3
Processor: Intel Core i5-2500@3.3GHz
Windows 7 64 bit

I would uninstall all nvidia drivers, shut down, remove the card, reboot, then install the drivers for the integrated graphics. Then reboot, and repeat the process but with the discrete video card the 2nd time around.

Out of curiosity, what PSU do you have to power your system?

guru3d has long since stopped hosting Driver Sweeper. Now its over on.

http://phyxion.net/item/driver-sweeper-290.html

To use this software, you want to uninstall the current drivers with the Add/Remove option in the control panel.
Once you have uninstalled, then use driver sweeper and then install the latest drivers.
Reboot between each step.