can only log in as root

Tried to boot from a Windows hard drive attached to a USB cable today- it didn't work, and coincidence or not Xubuntu (12.04) got crippled in the process. Couldn't log in at all, it just kept rebooting. I restored the old passwd file (the one the system had renamed passwd-), and now I can log in, but only as root. Have looked at all the other threads listed by the google search and none of them help. Have tried to create a new user (successfully), but then can't log in using it either- still only as root. Would quite like to be able to login as the user I could log in as this morning before Windows cursed my computer. Would also like not to have to reinstall the OS if possible, though that is an option provided it isn't going to ruin everything else.

Cheers!

Originally Posted by eeetee Couldn't log in at all

While the statement is important in your problem description, it does not help to give us an indication. From what you write, the only conclusion would be that you type in a user-name, then you type in a password and then, out of a sudden...

, it just kept rebooting

But I am sure that something is missing in between. Do you see anything written on your display?

Have looked at all the other threads listed by the google search and none of them help

Please identify at least one of these threads, which appears to address at best your problem, then tell us what you did to follow an advice, given. Only then, describe the way that the attempt has failed. It might give us an idea about what is broken.

Have tried to create a new user (successfully), but then can't log in using it either

What gives you the impression that the user account is fully functional and in which way does an attempt to log in ... fail?

Would also like not to have to reinstall the OS if possible, though that is an option provided it isn't going to ruin everything else.

Provided the system resides on its own dedicated partition(s), a new install should not harm your personal files, which should be safe on a different partition, where an installer does not (necessarily) have to do modifications.

Maybe you have a problem with your .Xauthority file take a look here → https://unix.stackexchange.com/quest...w-can-i-fix-it

https://www.maketecheasier.com/fix-ubuntu-login-loop/

If you have a problem logging in graphically, the first thing you should always do is go to a virtual console (ctrl+alt+Fn) and see if you can log in there. If you can, the problem is with the graphical display manager or something it depends on. If not, it's the password file or possibly PAM.