"The game "Counter-Strike" doesn't seem to be installed"

[RobMcLachlan]

If anyone else encounters this issue because their Steam Library is located in a different folder or on a different drive, here is a workaround:

Use MKLINK in an administrator command prompt (type cmd in the start menu and right click Command Prompt and choose 'Run as Adminstrator') to create a symbolic link from the folder coldemoplayer expects to the true location, e.g.

mklink /d "c:\program files (x86)\steam\SteamApps\common\Half-Life" "S:\SteamLibrary\steamapps\common\Half-Life"

That should be all on one line, e.g. mklink /d "link" "target"