If you change the order of the disks in the BIOS, then the computer will try to boot from the other disk. And that disk doesn't have the right MBR on it (if it has one at all), so that's why it didn't work.
In your case, the system is booting from the MBR on the hidden partition on disk 0. The boot code there then boots the operating system on disk 1. So if you change order, you have to get the computer to know where the active partition is (from the small hidden one now on disk 0 to disk 1), then you'd have to use something like BCDEdit to change the boot instructions so the loader would load Win 7 from disk 0 instead of disk 1 as it is doing now. And there might be more complexities.
Why do you want to change the order anyway? Disk order rarely makes any difference.