.net 3.5 offline installer Service Pack 1 runtime setup includes files required to run applications developed using Microsoft Visual Studio. If your application gives you “runtime error” whiling executing the executable file developed using Framework programming tools, then this application is required to be installed on system. Build incrementally upon .NET Framework 2.0, 3.0, 3.5, and includes .NET Framework 2.0 service pack 2 and .NET Framework 3.0 service pack 2 cumulative updates.
The .NET Framework 3 is included as part of the Windows Vista operating system; you can install it or uninstall it using Windows Features Control Panel. This redistributable package is for Windows XP and Windows Server 2003.