Inspiron 700m screen sizing problem

One day my computer's desktop icons got incredibly huge, and none of my images will fit on the screen.  My desktop picture won't fit, and when I get on the internet the text and pictures are so huge, it has to have a scrollbar at the bottom of the page.  I've tried display in the control panel and my internet options but nothing will work.  Help please!  It did this to m once before but it went back to normal on it's own after a couple days.