64 bit Windows: WTF: 64 bit dlls live in System32 dir, 32 bit dlls’s are in SysWow64

June 30, 2008

Here at Buildmasters, we have now moved all our development vm’s and other servers to 64 bit editions of Windows.

The 4GB memory limit is gone, and no more recycling IIS app pools and running out of virtual memory.

One thing to note however: The \System32 directory contains 64 bit dlls, and the legacy 32 bit emulation dll’s live in the \SysWow64 directory.

The is all done for backwards compatibilty, but it is very confusing.

Have a look at http://en.wikipedia.org/wiki/WOW64
for more info.

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