Deleted Photos Reappear

[perk]

There is probably a reason for this, but I am too much of a rookie to know what it is. Maybe someone can shed some light on this for me.

I have a low end Sony, I think it is a CyberShot P50 perhaps. This is what happened. I was reviewing photos and deleted several from the memory stick while it was in the camera. Later I took the memory stick to transfer to CD and lo and behold the deleted photos showed up on the CD.

Does anyone know why this would happen?

Thanks.