Do not worry my friend..Your Windows 7 is still there..
Do this: when you are in BT5, open up a terminal and type this:
1. os-prober (it will start reading the partitions available in the hard drive, you will see that WIn7 NTFS partition appears along with BT5..
2. update-grub (It will read os-prober and update the OS it found in the HDD, so next boot you will have your Win7 in the grub2 menu)
Then just reboot and the next time, in the Grub2 menu you will see all OS in HDD, in your case, Win7.