Problems with drivers.

[AsAsIn8eR]

I just bought a couple of days ago a videocard.An asus en7300gt top with ddr3 memory.I installed the drivers that came with the board and everything seemed ok until I ran a 3dmark 2001 where I got 7000 3dmarks this seemed.I thought it was my windows so I reinstalled it but when I did it had the same problem the same score.Then I opened accidentaly the task manager to restart and I saw that the CPU usage was at 80% in idle and that I didn't have any procces running with this usage.I reinstalled again thinking I did something wrrong and before I installed the video driver(I installed the motherboard driver(DFI Infinity UltraII M2) and it was 0% and right after I installed the video one I got 80%(after reboot).I tried the latest Big_Sam's moded driver too with it I get 50% usage.I tried the lates from nvidia I tried 92.91.All of these give em the same usage.What can I do?What could be the problem?The videocard uses IRQ 18