My computer wont go past the start up screen

Hello,
My computer wont go past the start menu. I have a windows xp disc but nothing prompts when I put it in. I press f10 f2 and it just tells me to put a password in. The previous owner says she didnt have to put a password in because it worked when she had it. I need to find a way to fix it without breaking the bank and taking it to have it looked at. How do override the computer system without having to buy a disc? Can you do f3 f4 f5 f6 f7 f9? Something that I can press while the page is starting up? Or do I have to buy a disc anyway.