I Installed Ubuntu 12.04 and after installation no Windows 7 entry shown.
Boot-Repair output : http://paste.ubuntu.com/1396793/
Some Windows boot files are missing. Probably there was a separate Windows boot partition that was erased when you installed Ubuntu.
"Grub2 (v1.99) is installed in the MBR of /dev/sda"
So basically you installed the grub to the only place the windows Bootloader can resist. Not a very good Idea.
The (from a Usability Poihnt of view) easiest Solution imho is:
Reinstall Windows MBR like this:
You need: A Windows Installation or Recovery Medium
This restores the MasterBootRecord. Grub will be gone (or at least not useable anymore) only Windows boots up.
Now reboot and install ubuntu again, but this time do NOT install grub directly to the sda mbr, but somewhere else.
Good luck, I recommend google and reading some articles about partitioning, double booting and stuff. It is worth the time, since it saves much in the future.