For Windows 7, 8, 10 and Vista you need to set WindFarm to run in XP SP2 compatibility mode.
There are at least 2 methods of setting the compatibility on Windows 7
1 go via Control Panel to Programs / Run program for previous versions of Windows. You may also find it via System & Security / Find and Fix Problems / Programs...
2 go to the program in C:\Program Files \ ReSoft \ WindFarmR4, right click on WFARMR4.EXE and select Troubleshoot compatibility.
If you are using 64-bit Windows then the program will be C:\Program Files (x86) \ ReSoft \ WindFarmR4
The program has a small flag on its icon when compatibility has been set.
Note that if you have installed the Release 188.8.131.52 (R5 pre-release) then you also need to set the same compatibility for WFRUNR4.EXE