There're two things possible:
- .NET is installed on the other machine, but a too old version.
You can try to install the latest version of .NET on the other machine, or set the Target Framework in your project file to a older version.
- .NET isn't installed on the other machine. You need to install the .NET Framework on the other machine.
If your other machine runs Windows 7, the .NET Framework 4.0 is installed by default, on a Windows 2008 R2 machine, the .NET 3.5 is installed by default and on a Vista machine and a Windows 2008 machine, the .NET Framework 3.0 is installed by default.