MSBee is an addon for MSBuild which allows you to use MSBuild to build your .NET 1.1 projects.
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Since the release of MSBuild in .NET Framework 2.0, a very frequent customer request has been to provide a means for MSBuild to build .NET 1.1 applications. This demand stems from users who want to use Visual Studio 2005 and .NET 2.0, but need to continue servicing customers who use .NET 1.1.
MSBuild Extras – Toolkit for .NET 1.1 “MSBee” is an addition to MSBuild that allows developers to build managed applications in Visual Studio 2005 that target .NET 1.1.
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Link: http://msdn.microsoft.com/vstudio/downloads/tools/msbee/default.aspx