Understand that we are volunteers here and don't need to help anyone with complicated workarounds who is demanding or less than fully cooperative.
Now that you've answered that you used your brother-in-law's Ultimate DVD to reinstall but want to use a student MSDNAA Pro key to activate it without having to reinstall, save externally a backup image of Windows 7: Backup Complete Computer - Create an Image Backup
. Also backup your files separately.
Now set a System Restore Point - Create
in Start Search box, rightclick on result to Run as Admin, browse to the following two keys to change them to exactly how they appear in the screenshot below:
click to enlarge
Using the Pro installer from desktop, run a Repair Install
Afterwards activate with your Windows 7 Pro Product key and save another backup image to use in place of future reinstalls.