Ijack :
You're right. OK, single-user mode it is:
1. Hold down shift whilst you start the computer. In a while you should see the Grub menu.
2. With the first item highlit, press "e".
3. Move the cursor to the end of the line that looks something like:
linux /boot/vmlinuz-2.6.32-28-generic-paeroot=UUID=xxxxxxxx-xxxx-xxxx-xxxxxxxxxxxx ro vga=794 quiet splash
4. Backspace all the way up to the space before "ro".
5. Type "rw init=/bin/sh", so now it looks like:
linux /boot/vmlinuz-2.6.32-28-generic-paeroot=UUID=xxxxxxxx-xxxx-xxxx-xxxxxxxxxxxx rw init=/bin/sh
6. Press F10 and let the system boot. Eventually you will end at a command line with a # prompt.
7. Type "adduser Fred" (for example) and press enter. It will ask you to type in a password and a few other details (you can just press enter on these details if you like).
8. When you've done that it will create the user and return you to the command prompt.
9. For safety's sake, type "sync" and then press return.
10. Do 9 again.
11. Do 9 again.
12. Press <Ctrl>-<Alt>-<Del> to reboot (I'm afraid that typing "reboot" won't work).
13. Once the system has rebooted and started up again you will be able to log on as "Fred" (or whatever name you chose) with the password you specified.
14. Enjoy.
Frankly, that's one of the worst solutions I've seen to this issue so far. It might solve the issue at hand right now, but also create a new set of issues.
1. The shift thing isn't a generic solution, it might work on most Ubuntu installs but it certainly won't for others like Debian. Now we do know it's from 2007 which means some early release of 8.04 or earlier. Other users with similar issues (or users with unhidden GRUB menus) might find this step confusing. Still, that's the most fair assumption in your instructions.
2. Most installs already have a predefined single user mode option in the GRUB menu, not that it'd help you very much in certain cases because of the next issue.
3. If the previous owner
did define a root password, you'd probably need that too.
4. Uppercase letters in the actual login name is strongly discouraged for legacy reasons, some utilities may not handle it too gracefully. While I didn't find any back in the days when I tried this on a SUSE 9.3 install, which utilities affected and any consequences are completely undefined.
5. You also forgot to tell adduser to create a home directory and a user group.
6. The "sync" command doesn't return until all disk caches have been completely flushed, meaning when you get your prompt back all data qued to be written at the time the command was issued is guaranteed to have been written.
7. If the "reboot" command doesn't work then you're either not root or have found a serious bug.
I'd aim to keep the solution as generic and simple as possible until we fully understand what we're dealing with.
(At this point I might even consider suggesting a full reinstall as an option since it's bound to be an old version of Ubuntu anyway, but that's not what the OP requested.)
The main thing about my solution is that it doesn't presume the OP has any control whatsoever of any account on the HDD while yours requires root access.
Sure, a chroot may be relatively tricky to set up, but at least it has a very high success rate since you do it from a system which you
do have complete control over. If you follow my instructions then I'd imagine the chroot is easier.