Windows loads slowly after installation of GT 430 with HD 5870  

I'm not sure if this belongs here or in the hardware section.

I recently bought an Nvidia GT 430 used on eBay for use as a dedicated PhysX card (Using Hybrid Physx mod) to work with my main Radeon HD 5870. I am running AMD 13.8 Beta drivers for the Radeon, and have tried both the latest Nvidia (320.49) as well as the drivers that work with the Hybrid Physx Mod (285.62) to no avail. All of this was done on a clean install of Windows 7.

The odd part is, everything GPU related would appear to run just fine, everything runs smoothly. The problem is disk access times, every time I try to open an application, or even a new explorer window, Windows takes about 10 - 15 seconds to load the program. When running just the Radeon, pretty much any program besides some games loaded instantaneously, and if I remove the Nvidia card, the former speed is regained.

Boot time also takes much longer, taking about 45 - 60 seconds when it used to take around 10 at most. And again, if the Nvidia card is removed, it boots quickly again.

I have never had this issue running multiple GPU's before, as I used to run a Nvidia GTX 670 (As main GPU), Radeon HD 5870, and Radeon HD 4870x2 without seeing a speed drop. After downgrading to just the 5870, everything continued to work much or less the same (FPS drops in a few games, as expected) and it wasn't until I added in the 430 that I got this performance hit.

I do not understand why the addition of the 430 would cause such a performance hit to disk access times, and any help would be appreciated.

EDIT: I should note that I have tried the GT 430 alone and it works fine.