This question has popped up a few times, so might as well make a thread about it.
If you try to install the modification via the installer exectuable and it fails with the "Valve's Steam not found" error, don't fret.
What is happening is that, to make installation as easy as possible, the installer checks to see if steam is installed and then uses the registry entries to figure out where it is installed. In the event the registry enties aren't there (normal cause is a bodged Steam install, recovering Steam from a computer backup, or if your Steam installation is incredibly old), the installer will be unable to find your Steam folder and quit out.
The fix for this and any other failed installer errors is easy enough though, but it does entail downloading the modification again.
Follow these steps to install the modification:
- Download and install 7zip. (if you've already got an archive application, you can skip this step.
- Download the SourceForts server archive from one of the mirrors on our download page.
- Extract the archive with 7zip, maintaining folder structure, into your steam/steamapps/sourcemods folder
- Restart steam and you're good to go!
Khuskan 
"Valve's Steam not found" and all other installer application errors
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