Is it perhaps a PCIe device? Could that be your GPU? It would definitely cause an extremely choppy / slow response time on the screen.
Beyond that, I can only recommend checking your HD or running SysInternals Process Explorer, found here: http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx
It will tell you absolutely every process that is running, even hardware interrupts and DPC's, which could be the cause of your slowness. Go ahead and check it out and see if it reports anything different about CPU / RAM usage.