Strong Name tool (sn.exe), does this tool copy the assembly into the GAC or only sign the assembly?
It only signs the assembly with a strong name.
What are the differences Windows Installer 2.0 and gacutil.exe ?
Windows Installer is not limited only to .NET. Windows Installer enables the efficient installation and configuration of your products and applications running on Windows.
gacutil on the other hand is limited to .NET assemblies which are deployed to the GAC. Contrary to Windows Installer the GAC is not designed to package entire applications but rather some reusable .NET components between applications. In order to be able to install a .NET assembly in the GAC it needs to first be signed with a strong name using the sn.exe tool.