One evening, while he was sitting in his chair and reading the latest paperback, Hans noticed something white behind the ventilation grill next to the fireplace. Carefully removing the grill he discovered a white envelope containing a diskette and a piece of paper. Excitedly he checked-out the disk, which contained a program. When he ran the program, he was greeted with the cryptic message:

X marks the spot

But what does X represent? A small text box on the screen seemed to be awaiting an answer. A little disappointed and confused, Hans unfolded the piece of paper and read the following:

T R O O C H X X I A O O
O P X O N F O O C T X O
H O O X L E X O I A O X
E H O O W T O X E U X O

What does X represent?