Error 5100 is a general error from the Microsoft .NET installer that can have a number of meanings:
- .NET has already been installed and target computer needs to be rebooted.
- The user running setup does not have administrative privileges
- A previous beta version is installed (the algorithm is similar to the one for the .NET Framework 2.0 described here, but the product codes are stored in the file named setup.sdb instead of install.ini)
- A later version of the .NET Framework 3.0 is already installed
- The OS that setup is being run on is not supported
- The OS that setup is being run on does not have the minimum service pack installed