Hello everybody,
I have some strange static screen bugs like this:
https://steamcommunity.com/sharedfiles/filedetails/?id=96851934
https://steamcommunity.com/sharedfiles/filedetails/?id=96851789
All graphics settings are recomended (marked *). Using:
Anyway, another source game working good.
Can I fix it?
dxlevel 90?
Regardless of how updated your drivers/directx is, that is a very old card (2003). You’ve probably just reached the limits of what it’s capable of. Aside from turning off some graphics options in the game to try and improve it, you are probably out of luck.
Shows as DirectX 9.0 in advanced graphic settings.
I have launched with -dxlevel 90 command. Now there are no line, but the game proces turns to slideshow 
Please notice: another Source games as HL2, TF, Synergy are working well and I have never seen that diagonal line. But I have seen some crashed textures and shows as magenta grid. Does it means, that some graphic abilities are turned off or I have damaged installed game?
Anyway, thanks for trying me to help.
It happened to me at the beginning of the game. I when into in-game option -> black mesa-> turned off HUD. Then the line went away.
Issue is though, when i get damaged by toxic water, it reappears. However i noticed that it disappears automatically whenever i passed the checkpoint.
gnrslash95, thanks a lot!
I have turned off HUD and line went away.
It’s no problem too see some crashed FXs and textures because of my old videocard, but this line is killing me
No problem. 
Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.