I have a program written on XP and it's a 32 bit program. I am familiar with WOW64 but in general would a 32 bit program run on a 64 os. Can someone explain the differences to me. Can WOW 64 be started as a 32 for programs? All the info you can provide would be appreciated. I am still a bit confused as to why some dll's from my 32 bit application will not install on a 64 bit OS or even possibly a WOW 64 .