Uninstall the current ones, if you have something like ATI Catalyst Center, uninstall that.It should work.
Download . Install it and run it. If you've got an ATi card, check 'ATi Display Drivers'. If you've got a nVidia card, check 'nVidia Display Drivers'. Click 'Sweep'. Wait for it to finish and you should be prompted to restart your computer. Save your work and press 'Yes' to restart now. Once restarted, locate the video drivers you downloaded earlier and double click the installer. Go through the wizard and they will be installed by the end of it. Don't panic if your screen goes blank during the process, that is normal.Congratulations, you have just updated your drivers.