If you want it to appear on the Start panel permanently > click Start > type
"Taskbar and Start menu" > Start Menu (tab) > Customize > Advanced (tab) >
under Start menu items: > check the Run command box > click > OK > OK.
You can add it like the old way by right clicking "start" then "customize".
Also, WinKey+R still works and the search box can be used as the "run" box;
just type the command and press enter.
You can enable it, but there really isnt any need for it. You can use the
Start Search bar just like a run line..although the Start Search is more
powerful than the old XP run box. ie type device manager in the search box
and press enter.