Clear Run Entries-an Easy Way

To Completely Clear Recent Run Dialog Entries follow the steps given below
1.Right-click on the taskbar and choose Properties, then choose Start Menu.
2. Select the "Classic Start menu" option, and choose the Customize button.
3.Now just click the Clear button to remove all of the recent documents and applications from the start menu
Once you've done that, hit Cancel and then Cancel again to make sure you don't switch to the Classic Start menu.
Note that this method will clear out everything… so if you just want to remove a single entry you have to edit the registry.