отсюда:
http://www.microsoft.com/windowsxp/using/64bit/russel_x64faq.mspx
by
Q. What is the SysWOW64 directory?
A. The WindowsSysWOW64 directory is where 32-bit system files are installed. 64-bit system files are in the Windowssystem32 directory for compatibility reasons.
и все