Ok, so when i start my pc it shows this :

U can write what ever u want and u cant.start the windows..UMM... You got yourself a PROBLEM. Do you SEE the loading screen that says windows xp?
if not when you turn on your computer the should be able to boot it from there.1) What is new or different since the last time everything WORKED properly (ie, new hw, new sw, virus, error, etc)?
2) Can you boot to safe mode?If your lucky you can fix this BIOS password issue by removing the CMOS battery and waiting a few minutes and reinstalling it or using the CMOS reset button or jumper on the main board.

Otherwise you have a bricked system. What is make/model of computer?

The older systems could be reset through the CMOS battery trick, but if a new system the BIOS chip needs to be replaced with an unlocked chip or a circuitry hack has to be used shorting specific PINS to bypass it such as what my BROTHER had to do with a certain laptop model that he bought off of ebay and paid some guy $10 for the bios hack instructions on which specific pins to short intermittently during boot up in which timing of the short condition was critical to success of it.