I did a new install on Ubuntu 12.04 and when it was finishing it did not install the grub loader and this installation was over a previous installation where the partition should have been formatted. The install will not install to any partition I have. And with no grub I am unable to get to my Windows 7
Boot from a Ubuntu live CD/DVD/USB or whatever, open a command line, and run the command
sudo grub-install /dev/sda (if you don't want GRUB on your primary hard drive, change sda to whichever hard drive you want it installed on).