Extreme Lag in TF2

[nicko11]

I've just bought TF2 and, since loads i know plays it. Anyways, when i launch the game, it recommends the highest specs available, so i launch it with that, and i'm having a terrible, terrible lag. And when i try to make it better by lowering the graphics, it's getting even worse.. Does anyone have a solution for this?

I'm capable of running every other source game on full load, and even Bad Company 2 on almost full load.

PC Specs:

Intel Core 2 Quad Q9550 2.83 GHz
XFX Radeon 5770
And 2 gigs of ram

 

[dalta centauri]

-dxlevel 81
Reinstall drivers
Lower your resolution and run in windows

 

[Kewlx25]

lag or low frame rate?

 

[nicko11]

-dxlevel 81
Reinstall drivers
Lower your resolution and run in windows

Why would i have to reduce the DirectX level, it's a problem with the core.