In Windows 7, right-clicking on the Windows Explorer Taskbar icon will show the Jump Lists. To access the shortcut properties, hold the Shift key down, right-click on the shortcut and choose Properties. The rest of the procedure is the same as in other versions of Windows.
To change the startup folder to (My) Computer, use this target path:
explorer.exe ::{20D04FE0-3AEA-1069-A2D8-08002B30309D}
Where the GUID {20D04FE0-3AEA-1069-A2D8-08002B30309D}
represents the My Computer folder.
For the Documents folder, use this target path:
explorer.exe ::{450D8FBA-AD25-11D0-98A8-0800361B1103}
You may also suffix the full path instead of using GUID. For example,
explorer.exe D:\Scripts