So what is the solution? We just have to get the 64-bit app to run as a 32-bit application. Once again, the app will crash or yield an error. If an application installer places a 32-bit DLL in Windows\SysWoW64, then later a 64-bit application tries to call that DLL, it will simply fail because, to the application, that DLL doesn’t exist.īut what if we get sneaky and copy that 32-bit DLL to the System32 folder? Our 64-bit app will find the DLL, but it will not be able to load it into its memory space (For a technical explanation why, see Why can’t you thunk between 32-bit and 64-bit Windows?). 64-bit applications cannot see or access the Windows\SysWoW64 folder. The flipside of this redirection scheme is that 64-bit apps are affected as well. When a 32-bit mode application runs under Windows 圆4 and wants a DLL from “c:\windows\system32”, Windows will “lie” to the app and give it the DLL from C:\windows\syswow64!
That seems backwards, doesn’t it? But it gets even more counter-intuitive. Windows 圆4 stores 32-bit DLLs in the Windows\SysWoW64 folder, while 64-bit DLLs go in the Windows\System32 folder. To understand why, we must understand how Windows separates 32 and 64-bit components. As far as the app is concerned, the DLL doesn’t exist. No problem, right? But what if that app makes a call to a Crystal Reports DLL that is compiled only as a 32-bit DLL? Trouble! That’s what happens! The application will not be able to find the DLL. Let’s say you have an application that easily runs as a 64-bit app under Windows 2008 R2 (which is a 64-bit OS).
Other applications and DLLs, however, can only run as 32-bit. Some applications and libraries (DLLs) are compiled in such a way that they can run either as native 64-bit or 32-bit mode. Have you ever had an application that seemed to initially run fine under Windows 圆4, only to have it crash or complain when performing a certain function inside the app? If you’ve run into this problem, take heart because the fix is really simple.īut first, it’s helpful to understand what happens when you run an application under 64-bit Windows.
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