On an old laptop first I installed Mint 11 LXDE, than I decided to give win 7 a try, installed it afterwards and grub menu was gone.
Then I tried with Mint live from usb to apt-get grub customizer, but I was without internet at the moment.
I solved this issue with Ubuntu Boot Repair Disc (https://help.ubuntu.com/community/Boot-Repair
I burned a Boot Repair Disc and it fixed it when run, he recognized both Mint and Win7.
When I booted into Mint again I fine tuned the grub menu then with customizer (entries, splash...).
But I know there is a simplier "update grub" method when running the live Mint from usb/cd/dvd, try to search the forum with these terms...