If the resolution you want to use is not provided in the drop-down list, you may need to do the following to add them. Be very careful when setting the resolution this way. Some monitors will be permanently damaged if you set the resolution too high. Check the documentation that comes with your monitor. Use this information at your own risk.
- Press Alt+F2 keys to invoke the command launcher
- Type kdesu "dpkg-reconfigure -plow xserver-xorg"
- Follow the instructions provided by the wizard
- Restart your system
Submitted by: Rage Callao