See if this post from Craig helps.
<quote>
I've also had this problem for the last few weeks, though happily I fixed it today.
This was in part with a call with MS support, and in part watching what sidebar.exe was doing with Procmon. I'm not certain that my reasoning is correct below, but you may get some mileage from it.
I suspect that an application had installed a duff copy of atl.dll (in my case I think it was from HP's IPaq Choice Points program - as procmon showed a reference to an HP directory when sidebar tried to start up).
I uninstalled the HP program to be sure. In the same way you may wish to search your machine to see if you have multiple copies of atl.dll before starting.
Upon the advice of MS support, I unregistered a couple of sidebar DLLs. This took me a little while as I didn't realise the DLL's are in Program Files\Windows Sidebar directory (windows search never found them for me, which is a touch annoying). Anyway to do this bit:
1. Start an elevated privileges command prompt
2. cd "\Program Files\Windows Sidebar"
3. regsvr32 -u sbdrop.dll
4. regsvr32 -u wlsrvc.dll
I then tried to re-register them, but it wouldn't work - I just got an error message. After some hunting around, I decided to first register (re-register ?) ati.dll. I didn't try to unregister it first, and as I definitely only had one ati.dll now, I didn't have to go looking for it to check I had the right one - but you might have to. I don't know what will happen in you unregister ati.dll so be warned.
So the next bit as I did it is:
1. From the same elevated command prompt (still in the C:\Program Files\Windows Sidebar) directory
2. regsvr32 ati.dll
3. regsvr32 sbdrop.dll
4. regsvr32 wlsrvc.dll
With the ati.dll done first, the Sidebar DLLs registered fine. Then I tried to start sidebar.exe again and it came up fine.
I had over previous weeks deleted all the sidebar settings and such like in an attempt to get it working, so I guess that might still be necessary as well - but my feeling is that it's really to do with the dll's above and the settings removal isn't important.
Hope it works out for you, because this was annoying the heck out of me for weeks.
Craig.
</quote>
Ref:
http://groups.google.com/group/microsoft.public.windows.vista.general/msg/e367f1868f0de080
Newsgroups: microsoft.public.windows.vista.general
From: SStarman <
[email protected]>
Date: Sun, 4 Mar 2007 06:24:54 -0800
Local: Sun, Mar 4 2007 7:24 pm
Subject: RE: Sidebar will not launch
--
Regards,
Ramesh Srinivasan, Microsoft MVP [Windows Shell/User]
Windows® Troubleshooting
http://www.winhelponline.com
After few month running vista, my sidebar suddenly gone and stop working. It
just like suddenly disappear but the sofeware still inside my computer. Just
cannot open and cant running. When I go to Programs/Accessories/Windows
Sidebar and click, nothing happens. When I go to Contol Panel/Windows
Sidebar I can see that Sidebar is set to start at Windows Start up but the
maintenance options are greyed out..please help me and give me some idea to
settle this problem
