.. and there are no minimize, maximize and close buttons in the window when I open one. Also I cannot move the window.
It's an ugly effect of Compiz; therefore I always use the cheatcode "knoppix no3d". Can you see the content of sda1 within PCManFM (2nd icon from left in the panel)? If no, get you errors with
Code:
fdisk -l /dev/sda
If yes, perhaps Testdisk may help you. It's not a tool for unexperienced users!