The only way to change your old passwd is the below.
1.Open a terminal and type sudo su.
3.Go and change your old password and try not to forget it again.
If you cant use your root user then you have to begin with a fresh image.
This is a bit awks, but I don't know how to open a terminal - do you mind telling me how?
Did u manage to change it ??
Well I can't get out of the login screen thingy so no... Like it's just code - and it won't let me do anything other than enter my login.
Did you change it from the originals?
What OS do you use
if it's raspbian the easyest method will be:
1) get the sd card and connect it to another pc
2) in the boot partition on the card edit the file named cmdline.txt and append to the end init=/bin/sh or init=/bin/bash ,the content it should be: dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline root wait init=/bin/sh
3) unmount the sd card put it in the raspberry (connected to a hdmi) and boot & w8 a little and you should see a prompt
4) enter the command : 'passwd pi' and put a new password
5) sync it an boot into OS: commands :
6) edit the file cmdline.txt to remove the init=/bin/sh
Alternatively edit the /etc/passwd to skip the password or get a new password in /etc/shadows (backup the files first)
Start with a new installation, change the original "raspberry" password to the one you want, read here about the raspi-config tool Raspberry Pi Documentation, enable to boot directly to desktop environment and finally start reading about terminal and how to configure your raspi.