Why did my GTX 670 go crazy?

Rather new PC builder here.
Recently i purchased a gaming rig w/ an XFX Radeon 7950.
However, today i decided i'd rather go with the Gigabyte GTX 670 Windforce OC, so i went to the store, returned the 7950 and came home with the GTX 670.

After setting it up, i booted up my PC. First thing i noticed: GPUtemp + GPU-Z weren't displaying any temperatures. Infact, GPUtemp didn't even recognize the card (however the computer notices it, just i can't get any temps.) So obviously i thought 'Well, i just need to install the drivers.'
So i installed the drivers. It wasn't until after they finished installing that i remembered that i still had my AMD drivers. Facepalm.

So i restarted my computer, however after the windows logo, my PC would not boot. The screen would just dimly flicker. So, considering the PC is newly built, i could save the trouble and just reinstall Windows 8. (Only takes around 5-10 mins anyway.)
HOWEVER during the install process, for a few minutes straight the GTX 670 fan went crazy. I would assume the fan went to at least 80%+. It was very loud, much louder than the 7950 when playing BF3/Crysis. I don't know if that's normal or not..

Card seems to be working fine after clean install.. no loud fan yet, GPUtemp says a safe 25 degrees C on idle (immediately after startup.) I haven't had a chance to play any games yet so i'll try Crysis tomorrow and see how it works.
So yeah, i'm guessing the boot problems were because of conflicting AMD + Nvidia drivers? But anyone know if the crazy fan was normal?

And if you're wondering about my case, i have a Zalman case w/ 3 case fans running. Airflow is pretty good.