|this is probably a hardware problem with the keyboard itself. sometimes junk will build up under keys, causing them to "stick" when you press them, so even after you remove your finger, the contact is maintained.|
try dusting out your keyboard with some compressed air. if the laptop's under warranty, get a new keyboard. if it's not, you could either try removing keys and cleaning under them, or try purchasing a replacement keyboard online (laptop keyboards are the cheapest part of the build).