Try to pass the following commands thru terminal (hope u still access Mint Terminal)
sudo os-prober (probably it shows, Widows Chain loader) then pass as:
sudo update-grub
else boot with the Linux Mint disc and re-install Grub. It should see the windows partition and add it to the boot menu.
Hope it will restore the boot menu as u desire. If it does not work, then
fdisk -l
parted -l print (probably it shows partition no.1 for windows) then pass
grub-install /dev/sda
And reboot hope it will work.

For better info see here:
www.sevenforums.com/backup-restore/62209-remove-grub-restore-windows-7-a.html

Just reboot the machine and a menu should appear that lets you choose. If not then follow the instructions in this link:

https://help.ubuntu.com/community/Boot-Repair