external monitor

Hi, I've added an external monitor to my aging Imac 17' intel core 2 white. Because there are vertical lines on the screen. Using a mini dvi cable and samsung via vga. Here is my query. The desktop shows but no dock or icons. Should I try to reinstall the os and see if the icons and curser et al show up? Or is there something seriously wrong with this machine. I've read stuff about video cards or something overheating. Other than that she runs fine. I think I can take it to the apple store for a free estimate and then decide it its worth it to fix it.

Sorry for the long questionz

thanks,

You need to set the external display for "mirror" mode not extended desktop as you have it now. Once it's in mirror mode you'll be able to see the entire desktop. No need to reinstall. Make the change from System Preferences, Displays.

There are no vertical lines on the external?

chscag has it - for more info, you can check out the sticky and head for Post # 2, Item # 3.

Thanks alot I will give that a try. No there aren't any lines on the external monitor when attached to the imac. I'll let you guys/girls know if this works. I'm such a newbie lol

I hope I can contribute to this board as time goes by. I will do a follow up post over the weekend as I won't be back til Sunday.