Unable to change password

Hi Im new to Ubuntu , very green, finding my way with the whole linux thing . I recently iNstalled dual boot on windows desktop PC , 2 days ago latest version of ubuntu. I was running the desktop from a usb and trying Ubuntu out. Then i installed Ubuntu as a dual boot . I set up password as part of installation. I set to no password required for login. when i tried to install software i entered password to authenticate and it was not recognised? Many attempts later i tried to reset password. from root menu i followed guide which suggested – mount -n -o remount, rw / passwd (name) When i installed dual boot the USB with tryout was still in PC has this caused a problem , i see two listings for ubuntu in root menu when i get to the new password part the keyboard does not type ? Any links or suggestions much appreciated , there seems to be a variety of ways of fixing this but Ubuntu is now requiring a password to login so i basically have a massive partition on my pc that i cannot use ? Thanks

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