odd environment lighting problem

I am having a slightly odd problem sincing installin9 fs9 onto my new computer. The problem concerns the environmental lighting, for example on aircraft and scenery objects isn't showing always. If i make a change in the diwplay settings e.g. render to texture or T&L it works again but only until i bring up a menu (alt) or open the map view. After returning to the flight the lighting disappears and will only return after going into the settings again. The machine is perhaps not i deal for fs being a dell laptop with a radeon xpress 1150 card and vista so i cant have all settings on full. Anybody have any ideas on what is happening and have a fix?Fighterpilot