Now when I bought my laptop the touch pad scroll was working fine until recently. I suspect that Windows changed the mouse drivers to default drivers, resulting in the scroll not working (Correct me if I'm wrong).
Just remove both mouse & touch pad from device drivers & restart the system & try again! It should get default drivers & work!
If this is not working, try downloading a latest driver from HP/Touchpad Manufacturer's site & install & restart & try again!