Manasa,
This answer DOES NOT WORK. My "Auto arrange icons" has been unchecked for 4 months -- ever since I got crappitoony Windows 8 and started having this problem and checked this site -- and STILL, my icons rearrange themseles periodically, for no identifiable reason.
Hey, you sorry excuses for engineers at Microsoft: FIX THIS ALREADY. WINDOWS USERS HAVE BEEN COMPLAINING ABOUT THIS FOR YEARS. I HAD A MAC LAPTOP FROM 2005-2010, AND ITS VERSION OF WINDOWS ENABLED ME TO LOCK THE ICONS ON THE DESKTOP. BUT MY PC WINDOWS 7 AND WINDOWS 8 HAVEN'T ALLOWED IT.
IT'S PRETTY OBVIOUS THAT PEOPLE WANT TO BE ABLE TO KEEP THEIR ICONS IN ONE PLACE. I MEAN, YOU-AT-MS DON'T LET YOUR MENU OPTIONS SLIDE AROUND. PEOPLE DO NOT WANT TO WASTE TIME LOOKING FOR THINGS THAT THEY HAVE PURPOSELY ARRANGED IN AN ORDERLY WAY. THIS IS JUST COMMON SENSE.