While installing Ubuntu, the Grub will detect any other operating system itself, but some time grub will fail to do such thing,
Manually Edit Grub Loader: -first try this
Manually editing Grub loader is easy thing you need to edit grub/menu.lst and grub.conf in order to modify the list, i was posted here with Topic of 'How to Recover Grub...' it'll work with windows vista as well.
If grub/menu.lst and grub.conf dont exist in your /boot/grub folder. you should Reinstall Grub loader .
But the reinstalling of Grub is mostly not possible while running same OS. - Getting worry?
don't worry about this we can reinstall GRUB by live Ubuntu ;)
To Re-install GRUB Loader:
To reinstall GRUB loader you should need a live CD of ubuntu.
- Boot your computer up with Ubuntu CD
- Open a terminal window or switch to a tty
- Type sudo grub. Should get text of which last line is grub>
- Type "find /boot/grub/stage1". You'll get a response like "(hd0,1)".Use whatever your computer spits out for the following lines.
- Type "root (hd0,1)", or whatever your hard disk + boot partition
numbers are for Ubuntu.
- Type "setup (hd0)", to install GRUB to MBR, or "setup (hd0,1)" or
whatever your hard disk + partition # is, to install GRUB to a
- Quit grub by typing "quit".
- Reboot and remove the bootable CD. Thats it!
If they not listed on boot menu, You may need to go step one for Manually editing the menu.lst file (after reinstalling grub on same partition of linux will put menu.lst file on grub folder so don't get lose to try first step )