need for speed most wanted, having problems installing demo

Hi I am trying to install the need for speed most wanted demo on my machine. I have DL it from the Eaplay site and Gamearena.

When installing the demo I keep getting a message saying I do not have directx 9.0c. I have the latest directx installed and have checked that there are no problems using the directx diagnostic tool. I have tried two different downloads for the demo.

BF2, HL2 and track mania all run fine.

Any ideas?

System specs. P4 3ghz 1024.00mb sp2.
Asus P4P800
Nvidia gforce 6600gt

Cheers.