All you needed to do was System Restore to before the problem, not reinstall the OS. It's not even possible to reinstall the OS accidentally since you have to select Install Now and choose the partition where to install.
If you chose the Windows 7 partition it overwrote the old Windows 7. Your old Windows 7 is either lost or may have been stuffed in a windows.old folder in the C drive root. Check now.
Once we see the Disk Mgmt screenshot we can see better what has been done. Do you still want to keep the Dual Boot intact? You may need to set up Windows 7 again after rescuiing your files from windows.old.
There is a way to restore a Windows 7-based computer to a previous Windows installation by using the Windows.old folder
however it is very complicated and not always successful.