The .Net Framework is a powerful development system for Windows created by Microsoft. Our software uses this new system, so the .Net framework must be installed on your PC to run. Microsoft is heavily promoting .Net to all its developers, so more an more applications are using it every day. Installing it will mean you'll be ready for these applications as well. You can learn more about the framework
Only Windows Vista currently comes with the newest version of .Net required, so if you haven't installed it already you'll need to do so.
The .Net Framework is a free 23 MB download available from Microsoft. The easiest way to get it is from Microsoft's page. Do a "Custom Install" search, and check the "Optional Software Updates" section for the .Net Framework 2.0
If you are unable to use Windows Update, you can also download a separate installer from Microsoft.