I dropped my samsung wb 750 on pavement. When I turn it on now the lens zooms to the farthest length and comes back in. I tried using a hair dryer to blow sand particles out but it doesn't work. I know its something inside the camera because the lcd still works perfectyly. Any ideas on how to fix it other than sending it back, buying another one or getting a repairman?
It is very likely that the camera has suffered internal damage which, unless you have some quite specialist tools to hand, you won't be able to fix yourself. It is more likely to be mechanical damage than dirt or electronic failure, so the lens is unable to lock in place or there is something else out of place. The problem is if you strip it down yourself you will have problems trying to put it back together correctly unless you have lens wrenches and a collimator (a device that enables you to set the lens for infinity focus whilst putting it back together).
As the cameras is quite old and not worth much on the used market I would suggest replacing it as your best, and only economical, option. If you have household insurance they might cover it.