Convert UE 4.7 project

I am trying to convert UE4.7 project to 4.8.
I have been trying to right click on the “Unreal Engine Project File” and click on “Switch unreal versions”.
After that I opened Visual Studio and trying to run the engine with it, but I am getting the folliwing error:


How can I fix it?

Ok solved it, I had to turn the program to win64 and not 32. but why? Is it limit me? how can I build the program with 32 bit?