I need help with my psp PLEASE !!!?

okay so I pulled the memory stick out of my psp and I put it in to my computer, and my computer did something weird to it and so after it was done I ejected it and put it back into my psp, but now I don't have a menu !!! it is completely blank, and I don't know what too do ? how do I get my menu back .... can any one help me ???