Not very helpful, maybe, but did you have a reason for needing to disconnect the XP installation?
It is a very awkward way to carry out the procedure.
As you have a clean installation of 7, I would suggest you reconnect the XP drive and install W7 again. It will , in the process, install a dual boot for you. You might have to reconfigure the boot.ini, maybe not, but this is easily done with a third party program such as Easybcd.