Go to the tab "settings" in Display Properties, and play around with things there....change the screen resolution, colour quality etc.

However, By the sounds of things I think your monitor has simply just had its time. My 17" TFT has been fine since I was 11...but i guess yours has less luck.

Actually, come to think of it, this has happened before to another TFT that we used to have. The ghosting came with old age, but to fix it for a decent period of time, dad or I would just bash it at the back or the sides and it would come good.