:- Digi ESP is not officially supported on Windows 7 64-bit Host.
The Solution explained here is only a workaround which may or may not work depending on your privileges on Host Machine.
Make sure that you have applied all latest patches. Double check by starting Digi ESP -> Package Manager (You should be having an Internet connection)
If all patches are applied then make sure that you have followed the instructions mentioned in Installed NET+OS 7.5.2 and all updates but getting build errors like >> multiple definition of ***Mesh***
Right Click on Digi ESP shorcut on desktop and go to Properties -> Compaitability
Run this program in Compaitability Mode -> Win XP SP2
Privilege Level -> Run this Program in Administrator Mode.
Go to C:\cygwin420\bin and apply the settings mentioned in point.3 seperately to executables > make.exe , gcc.exe, g++.exe