Right Click on your Desktop and select properties, click on Settings Tab then
on Advanced Button in the bottom of the Window right corner.
On Advanced properties click on Monitor Tab and you will see Moitor type
click on Properties and do your changes.
Another solution if you have LCD Monitor there are sets of Functions Buttons
on the Bottom Panel Window of the monitor something like [+] --- [-]
[Auto]---- [Exit] and so on, you can make your changes from there.
HTH
Please let us know
Regards,
nass