Option 1 - From Start Menu
1. Right click on the Start button -> properties.
2. Uncheck the Store and display recently opened items in the Start menu and the taskbar box, and click on Apply.
4. Click on OK.
Option 2 - From Windows Explorer
1. Delete contents of this folder:
C:\Users(User Name)\AppData\Roaming\Microsoft\Windows\Recent Items
Option 3 - From Registry
1. Paste this in a notepad -> Save it with the extension ".reg" and double click it.
[-HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\RecentDocs]