I should not have enter so fast, I wanted to install Ubuntu next to Windows 7, but by default it wipes out the boot sector of the main drive. Argh. Now I can't get to Windows (for all those wonderful games?!), so what to do?
I don't know if this advice from ubuntuforums will work, but they say you just need to figure out which drive has Windows (eg /dev/sda)

sudo software-properties-gtk -e universe && sudo apt-get update
sudo apt-get install mbr
sudo install-mbr /dev/sdX

I think this may install or recover from a Windows USB that lives boots into recovery mode (I'm not sure where to get one of those) but if you have a working Windows 7 then you can make it happen from the System Recovery tools