To add a folder to the taskbar, right-click on the taskbar and choose the Toolbars menu, and then click on New Toolbar.
Find the folder that is needed… for example.I shall select the "Computer" icon and then click on Select Folder.
Now you can see the Computer folder on the taskbar. If you click the little arrows it will pop up and let you browse through all your drives.
I always add the Desktop to the toolbar as well.
For Windows 7,use the exact same procedure.