I've read several answers to related questions here, but have not found one that matches my situation.
I assisted a colleague to reinstall Windows 7 from a recovery partition. We then booted into Windows, shrank the Windows partition (/dev/sda3) and the installed Ubuntu 12.04 (we partitioned the remaining space into / (sda5), /home (sda6), /swap (sda7) and free space for another Windows drive later.) I specified GRUB to install to /dev/sda. /dev/sda1 and /dev/sda2 were recovery/system partitions.
After rebooting, grub showed the Ubuntu boot options in the menu, and an option for a Windows recovery on /dev/sda1 and a similar one for /dev/sda2. It did not show an entry for Windows 7 on /dev/sda3. I booted into Ubuntu and ran sudo update-grub, but this failed to detect Windows on /dev/sda3. I checked the contents of /dev/sda3 and Windows is still there.
I hope I can resolve this soon, as this is not a good first impression of an LTS release to someone who has just decided to start using Ubuntu/GNU/Linux!
Best Answer
It turned out that one of the two entries in the existing menu was actually an entry for Windows 7, so the solution was to try both of the entries (while being careful not to accidentally start any actual Windows recovery operations). I'm writing this as an answer so that it can be accepted, but I'd also recommend filing a bug report about the mislabeled Windows entry by running
ubuntu-bug os-prober.