Why doesn't Windows 7 Ultimate (64-bit) contain folder system64 like system32 in xp?

I don't know about vista. I never used it. I just moved from XP (32 bit) to Windows 7 Ultimate (64-bit). I was expecting c:\windows\system64 directory similar to c:\windows\system32. Why is still entire system is located in system32? Why isn't there any system64 directory?

Solution 1:

Backwards compatibility reasons. A whole lot of applications assume things they shouldn't assume and hard-code paths. And yes, that includes 64-bit applications. So on 64-bit Windows the folder system32 actually contains the 64-bit versions of DLLs. For the 32-bit DLLs there is the folder SysWoW64 which is what 32-bit applications see as system32.