How can i change my screen resolution if my desktop is too big to fit on my screen?

my son and his cousin were fooling around on his computer and somehow set the screen resolution so that everything wont fit on the screen. How can i restore the screen if i cant see the whole desktop. Please help, frustrated!How can i change my screen resolution if my desktop is too big to fit on my screen?
Right click on your desktop and select ';Properties';

Choose the ';Settings'; tab

Under ';Screen resolution'; - move the slider so the numbers get larger

Click ';Apply';

Windows will ask if you want to keep these settings - select YES or NO - depending on if you like the way your desktop now looks. After you are done, click ';OK'; on teh Display Properties window to close it.