Account confusion


I reinstalled Mountain Lion, and after restarting was confronted with four different account names (three of them different ones I've created for myself. I've tried logging into all of them, and the passwords appear to be correct because the box doesn't shudder as it normally does when an incorrect password is entered). This is what happens: I enter the password, the screen goes blank for a second and then returns to the screen with the accounts. I simply can't get into my system to do anything, and don't know what to do. Any help appreciated: I have to get my MacBook up and running again by tomorrow.
Did you try the recovery?
From Apple:
'OS X Recovery includes a built in set of utilities as part of the Recovery System. To start your computer from Recovery, restart your Mac and hold down the Command key and the R key (Command-R). Keep holding these keys until the Apple icon appears. This indicates that your Mac is starting up. After the Recovery System is finished starting up, you should see a desktop with an OS X menu bar and a "Mac OS X Utilities” window’
Hi Cheryl
Excuse the late reply. I decided to go ahead, reinstall, and tidied up my User list. Things are a lot more manageable now and working perfectly again. Thanks for your incredibly speedy reply and all good things