I want to upgrade my Mac's Bootcamp partition from Windows 7 x86 to x64. I know it's got to be a custom install, but does anybody know if I can start the installation from an ISO mounted using Virtual CloneDrive? It worked for Vista x86 to Windows 7 x86, but I'm not sure if the initial file-copying installer for x64 is 64-bit.
Since there is no actual upgrade path from x86 to x64, this will not work. It requires a complete format and reinstall. You'll need to burn the ISO to a DVD.