The Monitor has nothing to do with the problem of games not working. If you did a System Restore *after* you reinstalled the graphics card, then you have undone the latest Drivers for your Graphics card.
Solution - re-download and install the latest Drivers for your graphics card from the Makers Site.
Try going back to the original drivers that came with the graphics card. If they worked previously then they should work again now. If they don't then you may have a problem with the graphics card itself.