Running GP4 in DirectX 8.1?

Was wondering if you could run GP4 using DirectX 8.1. I have the 9.0c version installed but I am able to run Team Fortress 2 in DirectX 8.1 with everything turned right up with no lag at all. I turn everything up with GP4 and get masses of lag. The thing that confuses me is the fact that TF2 has hell of a lot higher system requirements than GP4 so I was hoping that if I could get GP4 to run in DirectX 8.1 I'd be able to play it again until I get my new PC.

PC Specs:

1.7GHz CPU
2GB RAM
Some Intel thing graphics card thing.

Thanks