New system, yet not able to see much improvement!

All,
I am very very frustrated. Just bought a new system, put together myself with the following, yet, when adding transition, it is still slow mo! Why?

CPU: i7 3.5 GHz
RAM: 16G DDR3
GPU: GT240 (unlocked so PPro 5.03 recognizes as CUDA card)
Win7 Pro 64bits
Plenty of HDD (200G+ 150G + 50G free spaces...)

HELP!!

Thanks.

The only thing I have not done is reinstall from scratch. I simply let windows find all the updates and then, it starts working.

Perry