I've been working on this map for a while. Recently I also started work on a TFC map, so I made a separate configuration for that game in Hammer, and added tfc.wad and tfc2.wad - the textures for that game.
However, tfc2.wad has a texture file with the SAME NAME as a texture file in one of Half-Life's files - a texture I am using in my HL map. When I run it, it says "Cannot find tfc2.wad" or something like that. I learned you can fix this by copying said file into my half-lifevalve directory. I did so, and it fixed the problem.
I changed the texture file with the same name to a different texture file that does NOT have the same name as a tfc2.wad file, yet HL will STILL pop up with said error if I do not have the .wad file in the directory.
Why is this? I don't want to have to need this file for my map to run, as then people without TFC will be unable to play it unless they get ahold of the file.