Lenovo is joining the low-cost notebook parade with a $399 laptop. On Aug. 4, Lenovo released itsfirst low-cost notebook, or “netbook,” called the IdeaPad S10, which will have a 10.2-inch wide display and use Intel’s Atom processor. Lenovo, best known for its business-class ThinkPad notebooks, first introduced the IdeaPad line in January as a way to make headway in the red-hot consumer laptop market. The Lenovo IdeaPad S10 will be available in October.