If you really have tried everything then there's no point in suggesting you use Control Panel, Printers & Other Hardware, Mouse to check the settings. And neither is there any point in suggesting that you download a Touchpad Driver (Alps) and installing it and setting it up as you want it.
All that's left then is a computer doctor - perhaps the hardware has failed and needs replacing.
Help & Support - Computer Information will likely give you the model details.
Good luck...
Peccavi, October 2009