There is a workaround.
First have a look at this page: http://www.winhelponline.com/blog/wi...der-windows-7/
That tells you how to set the default start folder for your pinned taskbar shortcut to be root drive, My Computer or User Folder.
Then, assuming your Windows Explorer shortcut is the first pinned item to the right of the Start button, hit Winkey + 1. If it's the second, hit Winkey+2 etc. Up pops Explorer with your preferred start folder.
Hope that helps.