Forgot password for gnome

my uncle gave me a computer to see if i could find the username and password for it. I found out the username but i dont know how to get the password.

What distro and version of Linux is it?

If you have root on the box set the password for that account using the root account. If you are trying to reset root's password boot into single user mode (select this at your boot loader) then set the password there.

im not sure, all it says is "gnome" in the bottom right corner

what do you mean by bootloader?
it boots straight on to it without going through grub or anything.