Step 1 : Goto "RUN" and type "gpedit.msc"
Step 2 : A window will be opened (Group Policy).You will find two options in left side of the page.
Step 3 : Drop down the "user configuration" and again drop down sub menu "Administrative Templetes" and again drop down another sub menu "Windows Components" and click on "Windows Explorer".
Step 4 : Right click on "Prevent Access To Drives From My Computers" and then click on properties.
Step 5 : Click on the radio button "Enabled" and you can select any option in the menu.
Step 6 : Follow the same procedure for disabling it.