Did you mess up with your GRUB by installing windows after your Linux installation?
1. Boot from a Ubuntu Live CD
2. Open a Terminal. Login as Super User (execute the command sudo su )
3. Type “grub” to get GRUB prompt.
4. Type “find /boot/grub/stage1″. You’ll get a response like “(hd0)” or in my case “(hd0,3)”. Use whatever your computer spits out for the following lines.
5. Type “root (hd0,3)”.
6. Type “setup (hd0,3)”. The other instructions write GRUB into MBR. This instruction writes the GRUB into linux root partition 3.
7. Type “quit”.
8. Restart the system. Remove the bootable CD.
You should be good to boot your system back into Linux.
