I should warn you, this almost certainly won't work!! It's not the case that any old C program can be compiled as either 32bit or 64bit and continue to work identically. It is possible, but doing this requires that the programmer write their code carefully and with forethought. In my experience video game programs are almost always coded specifically for a given hardware target and little thought is given to making it portable to other hardware, and that includes 64bit versions of the "same" vendor.