on start up, go to setup and see if you can start it in safe-mode, that way you might get to trouble shoot it, if not, call a PC repair guy.
Is that after the windows logo? I may be able to help
Right When the computer boots up try pressing f8 repeatedly til you get a menu. If this works, go to safe mode and see if that works.
Would need more information to even begin to help. laptop or desktop? for starters.
get a new lap top....or...go to computer doctor....