Usually Ubuntu install in the grub menu this option:
title Ubuntu 8.10, kernel 2.6.27-7-generic (recovery mode)That text is part of my /boot/grub/menu.lst of my Ubuntu Linux, so first go to the easiest way to recover the password in Ubuntu.
kernel /boot/vmlinuz-2.6.27-7-generic root=UUID=393ac665-f5c2-488d-b601-b59ba1d5675b ro single
1. Reboot your system
2. When it is starting, press ESC to get the grub menu
3. Select the option that says (recovery mode)
4. In the next dialog select the root prompt, and get access to a console shell
passwd admin-usernameRemember to change the bold text by your username in Ubuntu, the one that has admin rights.
6. reboot your system, and you are done!
Now Going to the not so easy way, in case you do not have the recovery mode option.
Follow the same procedure as above until step 2.
3. Press e to edit
4. Select the line that starts with kernel...
5. Press e again.
6. Go to the end of the line and add single
7. Press ENTER
8. Press b to boot that kernel, with the single option.
9. Change password, and reboot.
Hope it helps.