Can't enter windows XP screen

Hello,
when i turn on the computer, the CPU seems to be making a beeping noise and just goes "toot toot toot" every 2-3 seconds. Nothing is displayed on the screen. It doesn't enter the part where the screen is filled with values being loaded (before the windows XP logo displays). do u know what's wrong with it? is it a hardware problem or a software problem? the last time i shut it down it was just fine and when i opened it again, all this happened. please give some advice on what i could do about it. thanks