Touchpad problems; automatically clicks.

Hopefully I can explain this.

On random occasions, whenever I move the mouse, it moves to the side/bottom & disappears & when I move it again, it automatically clicks everything.. such as highlight the page, open page source, etc.  It seems the only way to stop it is to do ctrl/alt/delete.  It also happens when I play WoW if anyone is familiar with the game; I move the mouse & sends my character running & when I move the touchpad it automatically moves my camera settings. Only way to stop this is to the 'windows' button or ctrl/alt/delete.

I've reduced the speed, double-clicking, and any other settings that I could think of.  Also did a virus/malware/spyware check and it's clean.

It's a dell inspiron 1501, 6 years old. This started two weeks ago. 

Any ideas?

Thank you.