Collapsed Boxes at Top Right Corner of W

My brother has recently purchased a Dell PC. He is running Windows 98 OS.
EVERY window that he opens on his computer, the three “boxes” in the upper
right hand corner of the window (Minimize [_], Maximize[-], and Close [X])
have a width that is about 2 mm wide. You can not see any of the symbols
in these boxes, however, if you select (click on the tiny box) with the
mouse, the box does what it is suppose to do. How do we get these boxes to
return to their “normal” size????

Do we have to reinstall the OS from the CDs???? Or is there some other way
to fix this problem????

Thank you,

Mark