scrolling on my ux31e

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Windows

hi,
i just bought an asus ux31e, it's a good machine but I have an issue with the touchpad. Particularly with the scrolling while i watch pictures on internet (like on fb or book scans). When i scroll down, it jump to a few pages/pictures forward...i think it come from the fact that the scrolling move up-down and left right simultaneously, like on an ipad. I tried to find out how to remove this, but can't find how to do this. Is someone who can help me?

P.S.: I looked on a few websites, and somes show screenshot of ELAN's options on the scroll, but i haven't this setting.

Thx!