Where are the shortcuts for the Windows 7 Taskbar stored on disk?

Taskbar shortcuts are located in: %AppData%\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar.

You can also add the "Quick Launch" folder to your task bar as a toolbar to re-enable the quick launch feature.

Hit the Windows key and paste

%APPDATA%\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar

to find the pinned taskbar items, or simply

%APPDATA%\Microsoft\Internet Explorer\Quick Launch\User Pinned\

to see the folders for those and the start menu items.

If you're having trouble getting Windows to remember pinned items you may need to remove the Favorites registry key at HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Taskband\.