Ubuntu won't install on my laptop

[Xeginy]

I have an Asus 900 series laptop, which is currently running Ubuntu 8.10. I got the Laptop from a friend, who got it from another friend, etc...it's been passed around quite a bit the last few months, so I can't find anyone who knows the administrative password. I can't change the password myself, so I was told to just install the newest version of Ubuntu (9.4). I have it on a disk, I have an external disk drive, but when I try to boot up my computer from the disk, it simply goes to my regular desktop. It recognizes the disk, but when I try to open it, it asks for an admin password. Is there anything I can do?

[utnubuuser]

try:
http://www.fixya.com/support/t1916852-asus_computer_password_reset

[Xeginy]

I don't know how to take the battery out of my laptop. I've gotten this advice before, but I don't know how to do it. Any idea why the computer doesn't seem to be booting from the disk?

[Xeginy]

Okay, nevermind, I figured out how to take the battery out (turns out it's not that hard)

Problem is that it didn't work. I took the battery out, put it back in, and then turned the computer back on. I pressed F9 (like the instructions said) and absolutely nothing happened. The computer booted up like normal. What am I doing wrong?