Start | Run | Type regedit, and click OK | Expand the following branch...
HKEY_CURRENT_USER | Software | Microsoft | Windows | CurrentVersion | Explorer | Advanced
Check the Start_EnableDragDrop DWORD in the RH pane for a Hexadecimal Value data of 1 (right click the above DWORD Value name and select "Modify". In the Edit DWORD Value window that opens, check to make sure 1 is the listed value in the Value data field)
Next, expand the following branch...
HKEY_CURRENT_USER | Software | Microsoft | Windows | CurrentVersion | Policies | Explorer
Right click in the RH pane and select New-->DWORD Value, then name the new DWORD NoChangeStartMenu. Right click the new DWORD and select "Modify". Make sure the Hexadecimal Value is 0 in the Value data field.
In addition, check the following setting...right click the Taskbar and select "Properties" | "Start Menu" tab | Make sure the "Start menu" radio button is selected, then select the "Customize" button | "Advanced" tab | Check to make sure "Enable dragging and dropping" is checked.