You installed a new version of Windows 7, just to discover that Windows made a 100MB partition on your old harddisk, so now you can’t boot without this harddisk….

I was looking for a solution to this, most solutions suggested to delete the partition and un-plug the old HD and then using the Windows CD to make a new system partition.

Well, I found a better solution and it worked out just fine.

If you want to keep a special partition for your boot files, start by making a 100MB partition on your C: drive (assuming Windows is installed here).

It is recommended to make a backup of your harddisk before following the next steps.

Now follow these steps, remember to use the correct disk and volumes.

1. Click the Start button, then in the “Start Search” box, type “CMD” but do not press Enter yet.
2. In the list above the search box, under “Programs”, right-click on CMD and choose “Run as Administrator” and click “Continue”.
3. In the open console, type the following commands and press Enter:
   diskpart
select disk 0 \\I assume that the 100MB partition is in Disk 0
list vol
select volume 0 \\I assume that the 100MB partition is installed in "volume 0"
inactive
select volume 1 \\I assume that the OS is in "volume 1"
active
exit
4. Type in CMD (still in administrator mode):
   C:\windows\system32\bcdboot.exe C:\windows /s C:

It should prompts that the command line is successfully. Restart the computer. The boot files should now have been moved from the old HD to the new one.

Note: if you put the boot files to a new partition, remember to set your OS volume to active again.