Build in .net 1.1 using Visual Studio 2005?
To target VS 2005 using the older .net framework, try Jomo's work around - http://blogs.msdn.com/jomo_fisher/archive/2005/04/22/410903.aspx
Also check out Robert's workaround, although it's not working for me:
http://www.longhornblogs.com/robert/archive/2005/06/03/14156.aspx
http://www.hanselman.com/blog/BuildingNET11ProjectsUsingVisualStudio2005.aspx
The MS supported version is coming soon:
http://blogs.msdn.com/msbuild/archive/2005/11/09/490817.aspx
http://blogs.msdn.com/clichten/default.aspx