SonyVAIO pcg-frv37 Backlight lamp stops on LCD display on OS starting

I have a old SONY VAIO (gift from american friends)
At the moment (after I install Windows XP updates) after restart,on starting of OS, backlight lamp stops on laptop LCD display. There is OK in DOS mode. I’v try to reinstall win (recovery kit) bet no positive results – lamp stop on OS starting.