I have installed .net framework on my PC but many applications are not running says .net framework not installed yet the required versions is installed
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            I've found http://www.hanselman.com/smallestdotnet/ to be useful in working out which version is installed and what is missing.
                  harriyott
                   2010-07-13 07:24:57
                
              
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            Check HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP key and c:\WINDOWS\Microsoft.NET\Framework\ to be sure that specific versions really installed. If you'll not find any you need, then try to re-install.
                  Eugene Cheverda
                   2010-07-13 07:25:02
                
              
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            Uninstall it, and reinstall it. That has worked for me in the past. And double-check to make sure you have 3.5 SP1, not just 3.5!
Hope that helps!
                  Kieren Johnstone
                   2010-07-13 07:35:51
                
              
                
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            you can try .net framework fix tool at the link below...
http://blogs.msdn.com/b/astebner/archive/2008/08/28/8904493.aspx
                  dankyy1
                   2010-07-13 07:55:05