I recently upgraded my main development machine to Windows 7. This involved wiping out my primary boot drive (Windows XP 64-bit) and starting clean. Before I wiped it, I did a direct disk-to-disk copy to a big external hard drive I have. While I have been able to migrate most of the necessary files without any problems, I was wanting to boot from it today to check a few settings. I plugged in the hard drive, rebooted, changed the BIOS to boot from USB-HDD first. But, no mattter what I do, it always boots from my primary drive to Windows 7. I do not see any kind of error message or anything.
How can I boot to Windows XP 64-bit on this external hard drive?