Urgent problem to be solved regarding display

im using hp compaq notebook working on windows xp professional. i done a small mistake by changing display properties in control panel and system asked to restart and i restarted. after that i saw the logo of windows started loading and my desktop display was blank. i dont know what to do. im getting initial display of my notebook showing hp notebook logo and windows starting logo and after my desktop sisplay was blank. please help me out of this problem. please help me.