I have all Windows 7 editions on my DVD. When I have mounted install.wim (and I have only one, 4 gigabytes), I see a complete x86 structure. But there is NOTHING AT ALL related to x64 edition. No SysWow64 folder, no 64-bit DLLs, nothing. I have searched everything. Where the heck could it hide 64-bit files?
Got it... I should have selected which image to modify. That seems to suggest that I have to modify all 9 images. What a big amount of pain in the @$$. Unless maybe modifying highest in the hierarchy (x86 Ultimate and x64 Ultimate) is enough. I sure hope so.