It was running lightning fast and since installing GTX 670 its extremely slower for the first 30 seconds after logging in. Windows starts up considerably slower than before too. Its been like this for over a month.
It takes longer for my hard disk to connect to Intel rapid storage I noticed. Could it be a problem with my HDD? When I was installing the GPU I re-wired the SATA cables about, they have always been cramped into the HDD's port and slightly strained/bent due to how its layed out. But I've read this happens a lot after installing a GPU
Did you move the HDD to a different SATA port after installing the GPU?
Can you re-connect to where it originally was? That may help. Seems like that may have something to do with it, or some services added to the startup menu as part of the drivers for the GPU.