If you read the instructions, you'd find that you need to right-click on sidebar.inf and select Install.

EDIT: Whoops, I didn't see ricktendo64's post from the email notification. Feel free to delete this post.

If you installed the sidebar using my addon or installer you can go to Add or Remove Programs and in the Windows Sidebar uninstall options you can use the Change button to reregister the sidebar libraries.

Manual register commands you can cut and paste into a run or cmd window

"%ProgramFiles%\Windows Sidebar\.\regsvr32.exe" "sbdrop.dll" "wlsrvc.dll"

"%ProgramFiles%\Windows Sidebar\sidebar.exe" /RegServer

I'm suddenly having the same problem with some gadgets like MultiMeter Dual-Core & Outlook Appointments only showing as a white box. However, the