No usb drivers/ ports working asus eee netbk

Hello, every time i try to use any device via usb port--i get the message-- drivers not installed. i have gone into device manager and on right clicking on the yellow flagged item--i get the message --update driver or reinstall driver..when i try to do that i get either error code 1 or error code 28 as well as message "access is denied". I have windows 7 starter pack on my netbook. My computer was working fine until July 2010--i have even tried to system restore but keep getting the same messages.
Please help!
psud