A while back at work I needed to install the SourceSafe client onto a desktop that had Visual Studio 2003, but not the SourceSafe integration. After a few posts back and forth here at the Microsoft SourceSafe Forum, I was able to come up with a solution.
1) Copied VSS\Win32 directory from sourcesafe server to local client machine in C:\Program Files\Microsoft Visual Studio\VSS\Win32.
2) Ran SSINT.exe
3) Opened Visual Studio 2003, opened a project from source control. It works.
4) Deleted everything from the local C:\Program Files\Microsoft Visual Studio\VSS\Win32 except: ssint.exe, mfc70.dll, msvcr70.dll, ssscc.dll, and ssus.dll. This is the same file list that is present on a workstation that had the integration installed from the SourceSafe CD.
5) Opened Visual Studio 2003, checked out a file, checked it back in. Works!
One comment that both the posters stressed is to make sure you have SourceSafe licenses for the machines the machines that you install the integration onto.