Portal: First Slice -- I need help!

[Spoo]

I've been trying to play Portal: First Slice for some time now, and it keeps giving me some error saying that I need DirectX 8.0 or above.  I have 8.0 (For quite some time no, actually.), and I've installed and re-installed 10.  Yet, I keep getting the error.  My Steam account is AkinariAT if you'd like to PM me there. 

 

[kaidus]

GPU details? Also check there isn't a line like mat_dxlevel 70 in your config (gamedirectory\cfg\config). If it's there set it to 80 (or 85, I forget).