What sort of file is it? Basic data files are pretty much platform-agnostic, but *.EXE files can be quite finicky. That said, merely going from a 32-bit OS to a 64-bit OS shouldn’t affect the ability to run a particular app since most 64-bit OSs have some form of backwards compatibility, at least to relatively recent predecessors, so if you could run it on a 32-bit WinXP box you should be fine, though if your old box was Win98 then it’s less likely, and if it was Win 3.11 you can pretty much forget it. So, could you please elaborate a little? Waht was the old OS, and what sort of file are you trying to work with?