Assuming, and it sounds the case, that grub2 is now installed, but Windows wasn't automatically added to your grub list, it should be fairly simple to fix.
First, make sure you have os-prober installed. (Both of these as root.)
apt-get install os-prober
Then update grub.cfg
grub-mkconfig -o /boot/grub/grub.cfg
And it should autodetect your windows install and add an entry to your boot screen. If not post back. We'll need to gather some more info.