Ok, here's the log output:
2009-12-22 15:28:26,820 [1 ] [INFO ] [DroidExplorer.Bootstrapper.Program] System Info: Microsoft Windows NT 6.1.7600.0 x64
2009-12-22 15:28:26,836 [1 ] [DEBUG] [DroidExplorer.Bootstrapper.Program] Starting setup with arguments: /log
2009-12-22 15:28:26,838 [1 ] [DEBUG] [DroidExplorer.Bootstrapper.Program] Mode set to install
2009-12-22 15:28:26,839 [1 ] [DEBUG] [DroidExplorer.Bootstrapper.Program] Checking for Minimum .net version
2009-12-22 15:28:26,842 [1 ] [FATAL] [DroidExplorer.Bootstrapper.Program] The requirement of .net framework 3.5 SP 1 was not found.
This is true for me: SOFTWARE\Microsoft\NET Framework Setup\NDP\v3.5\ exists. if it does, is there a value, named "SP" with a value >= 1?
I have English Windows 7 x64 Ultimate retail RTM
I've also installed Visual Studio Express 2008, SQL server express 2008 and MS ASP.NET MVC 1.0 if those are making the detection problem.
What you COULD do is to release a x64 version without the .NET check until you find a solution. (Let's call it the Window 7 x64 version because it won't need a check)
Thanks for a otherwise great software!