What makes old EXE files unusable ?

[rabir007]

Actually, what makes the Old exe files incompatible with old systems ?
Using different ASM or what ? Especially when you try an old game on new OS like Diablo 2 and Windows 7...

[Hell_Demon]

Old games usually rely on versions of graphics libraries that are simply no longer exist on the new OS.

[rabir007]

Old games usually rely on versions of graphics libraries that are simply no longer exist on the new OS.

Sooo, what if we re-configure the bytes in the game to the new versions of Graphics APIs ?
Or implement the old version (C+P) the dlls into the game folder...

[_corn_]

They might also rely on old kernel calls which do not exist in the current OS. Have fun C+P-ing the kernel calls.

[Hell_Demon]

If you have the code of the game it's doable in a short period of time, if you don't however it'll prove a very tedious task.

[Fovea]

No sane game programmer would directly call kernel functions (at least in this era, you have to go far far back before my statement would be invalid). The usual case is deprecation of API and changes in the API. If you go back far enough, there are changes in the executable file format itself and even further back there are even instruction set behavior nuances. This is all assuming your game was run on the same architecture and the same line of OS. It is a whole different story if there was an instruction set change (e.g. PowerPC to x86) or an OS change.