After getting Windows 7 x64 installed, I was having a problem getting a few gadgets to work correctly (like the Pandora Gadget). It turns out this gadget uses Flash, which only comes in a 32 bit version. The Sidebar is x64, and can't access Flash. Since there is no x64 version of flash (come on Adobe -- its time to bite the bullet!!), I started digging around for a way to overcome this limitation -- as luck would have it, Microsoft ships the 32-bit version of the side bar in the x64 versions. Now all I needed to do was get it to startup instead of the default x64 bit version.
Edit the following Registry Key:
\\HKCU\Software\Microsoft\Windows\CurrentVersion\Run\SideBar
Change the key to this: C:\Program Files (x86)\Windows Sidebar\sidebar.exe /autoRun
(The only addition is loading sidebar.exe from c:\program files (x86)\ instead of c:\program files\)
This should get you by until Adobe gets their act together!