It sounds like it's trying to start up a graphical login screen (by starting an X-Windows server) but that is crashing and putting you back into the command-prompt.
The thing you are looking at where is says “login:” is a login screen, albeit an old-fashioned one. So there's nothing to indicate that your partitions have been messed up.
What you need to do is disable X to give you a useable session. It will probably do this for you after about five minutes; if not then try typing 3 at the boot command-line (where you select to boot into Linux); this will boot you into runlevel 3 which does not use a graphical login.
Next, log in (type your usename and password) and run
(you may have XOrg.0.log instead)
Press > (usually shift and full-stop) to scroll to the end of the file, then look for any error messages relating to X starting up (up and down cursor arrows to scroll).
The easiest way to fix this problem might be to reconfigure your X server; various distros have different ways of doing this, but you might try running
(this is a standard but basic utility that ships with X, so comes with most distros; you will need to type your root password here).