How do you get to the grub2 os choice menu on a dual-boot installed Ubuntu

Hi when I dual-booted ubuntu on-top of my existing win7 OS(damn you closed source! but alas, I am a gamer and most games require win) SO when i run my computer it goes straight to win7 as apposed to taking me to the options screen. I recently totaled my computer trying to do this so I told the computer to boot directly to the SDA 2 partition(my win7 partition) it would be really nice if someone knew how to undo this therefore solving the problem. I really wanna use ubuntu especially gnome 3 but at the moment I cant even reach the dual-boot screen. I have lots of computer experience so fire up the tech talk. Until someone awnsers this I will keep trying to find a solution to the problem.

Thank you,
William McGreggor( I'm actually a twi'lek from ryloth)