My computer crashed and lost pictures....?

I have an HP Pavilion 742c with windows xp operating system that crashed a while back and would only show dark screen with flashing _ I turned off and was going to have looked at but let sit for about 4 months. My laptop froze on me and in desperation turned the xp back on to try it. It came on as if brand new computer. I went with it and now seems to work fine except none of my files or pictures are there any more. Is there any way to find those files or are they lost forever?