sync out of range

hie. i changed my setting display to the minimum size. i
taught of just have a test and have a look how it will
look if i set to the minimum size. now my problem is my
window can on but when it goes it, i can just see the
display of "sync out of range" i have tried many ways to
solve it.. please help me find a way to set the display
to 800 by 600 pixels back again.. i am not sure what
pixels i had set to but i knew it was the minimum one. i
couldn't see the the window screen at all.