Steam\userdata\SteamID\AppID isn’t a valid file path for me… after Steam\userdata\ my only folder option is labeled “176755873” and when clicked leads to more gibberish folders. Running Windows 10 and downloaded off steam. Please help. I have 0 sound in this game 
What is going on, is that you’re seeing a number that steam uses to identify a user, called your SteamID just like in the url above. If you only have one folder with numbers that had lots of numbers in it, then what you need to do is find the content id number of black mesa. If there is more than one then you probably have more than one user using steam on your computer and you’ll have to figure out which folder is who’s based on things like the number of games each of you own or other similar simple things like that. Now, what you are looking for, is called the AppID of black mesa, also just as stated in the url above in your repost. For me that number is 362890 and that may be the same for you so if you wanna try it skip to step 3.
-
To find the black mesa content id number, so that you can find the right folder to open, you have to go into your steam library. Once there right click on retail black mesa and select the option to “Create desktop shortcut”. Once you do that, go to your desktop and find the black mesa shortcut you just created. IF YOU ALREADY HAVE A BLACK MESA SHORTCUT ON YOUR DESKTOP(Skip to here) you obviously don’t need a new one.
-
What you do now is right click on the desktop icon shortcut you created and then click properties. Either under the tab that says details, or web document there should be a url that looks like this “steam://rungameid/362890”. The number you need to identify the folder you need to open to remove cloud files from is that number at the end of the file.
-
Now what you do is go back into that folder that has the number that identifies the steam user’s account, (within the filepath “Steam\userdata\SteamID”) and go into where the long list of folders is named with all sorts of different numbers, and you look for the one with that black mesa content id number, the “AppID”, which was 362890 for me, (which makes my filepath look like this "Steam\userdata\SteamID\362890 with my steam id missing for security.) You open up the black mesa folder id’ed by that number and follow the rest of the steps that you reposted above to clear out your cloud data as written in that nice list and you should be golden.
Have managed to fix this annoying issue by manually installing every Visual C++ redist from Microsoft; 2005, 2010, 2012, 2013, 2015. both x86 and x64.
Also on Windows 10 and I think 8 and 8.1, make sure the “Give me updates for other Microsoft products when I update Windows.” is ticked in the advanced options area of Windows Update because that will update visual c++ redists as well.
Steam cloud seems to have no effect on whether or not the music works after updating vcredist so don’t worry about that.
Hope this helps people still stuck reinstalling over and over again and turning steamcloud off and on again.
Installing and updating all the Visual C++ redist packages did it for me. Thanks for that tip.