Installing Windows 8 Developer with Windows 7

I have installed Windows 8 Developer on a separation partition and Windows 7 on the other partition.
But after installation, Windows 7 is no longer visible in the Operating Systems Selection.
I tried and researched for solutions on the internet and from tutorials but I could not find any.
Any suggestion on how can I fix the problem of the installation of Windows 7?
Does it involve the Master Boot Record?
