Sony VGN-U750P VAIO Read This First Manual page 37

Action Description
Scroll Push the multi-pointer while pressing the centre button (5) (the scroll function is available only with applications that support a
scroll feature).
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Your computer is also equipped with the up (1), down (2), left (3), and right (4) cursor keys and the Enter key (5) for pointing
operations. The cursor keys are equivalent to the arrow keys on the folding keyboard.
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Using your VAIO computer