Re-installing the GRUB menu in Xubuntu 12.04
This is quite specific to Xubuntu 12.04 which uses GRUB2, not GRUB.
There is LOADS of conflicting advice on how to re-install the GRUB menu once it has been trashed. Typically it is trashed by trying to install Windows on a Linux system, assuming the Windows will play nicely and make it a multiple-boot machine. Windows doesn't do that.
- Boot from a Xubuntu 12.04 Alternate CD (not an installation CD nor a Live CD)
- Use the boot repair option.
- In my case, since I want the Xubuntu on partition sda7 to be the default, I enter
/dev/sda7at the first prompt, then/dev/sdaat the second.