Your display preferences need to be changed.

Right click anywhere in a blank area of your desktop and then click on properties on the menu that pops up

when the window opens select the settings tab at the top

if the slide bar on the left reads 600 X 400 then you are either running in safe mode, you have accidentally changed the setting, or your video driver has taken a hike and you are running on the lame vga standard that is a windows default

change the setting by sliding the bar to the right until you reach 800 x 600 or 1024 x 768

it may ask you to keep the changes select yes

if the computer is running in safe mode then just reboot

if you have a laptop then reboot as they tend to reset themselves to the default for the screen

if none of this works or if you have no other selection and the bar will not slide or is grayed out then your video driver has failed or become corrupt

you can try to reinstall the correct driver or take the computer to a qualified technician (NOT BEST BUY) and have them do it for you

I hope this helps! Good luck.

Cindy