When I open black mesa and get it running, everything works perfectly except for 1.) A thin white line running from the upper left corner of the screen to the lower right. 2.) Random missing textures (Textures missing with purple-black checkerboard replacing them) Such as human eyes, the radioactive fluid, and most importantly, the entire screen goes missing texture when you become submerged. Could someone please help me with this issue, and please be specific such as tell if/how I have to uninstal the current copy. Thanks for the help.
Ok, so I’ve managed to find the BMS file, delete it. Then I reinstalled all the required files and checked the MD5 checksums (They matched perfectly) And yet when I opened the game the textures are still missing. I have also downloaded the faulty window’s update patch before redownloading the files. Can someone please help? Thanks
Did you try to verify sdk base 2007’s cache?
Have you read this topic (Q6a and Q6b in particular)?:
[FAQ] Semi-complete Black Mesa FAQ - READ FIRST
Adding an additional screenshot, of the missing textures, to your next post might help.
I remember something like this happening when trying to run the game with a low directx, which one do you have?
must run the game in direct x 9 only nothing else
Thanks for the help, now the missing textures and the whiteline are gone. All I need to do now is find a thread on lag reduction because the new dx level is lagging my game a bit. Thanks 
your very welcome
The best way to reduce lag is to put mat_picmip 1 in console and set the resolution to 640x480.
I’ll try that out. Hope it works because the game lags beyond functioning on the surface part of “We’ve got Hostiles” for some reason.
[Edit] Got it to work Thanks for the help so far everyone!