I had this problem with Windows Vista and I know what you're going through and it is a nightmare. but don't panic I'm not sure why your sidebar has decided to stop working. I would also guess that if you looked in services you would probably find it's not in there either. This was a common problem with Windows Vista where it decided to stop working for no reason as well. Microsoft was supposed to resolve this matter with Service Pack 1 but they didn't. Although I do recall this being resolved with service pack 2.
Okay please follow the instructions as listed below to the letter and pay attention to detail and try to concentrate. if you're a complete novice to Command Prompt commands than don't worry because I shall guide you through every single step.
Step One: Command Prompt- Open Command Prompt first by clicking on Start>All Programs>Accessories, right click on Command Prompt and then select run as Administrator. Now that we have Command Prompt open we shall move onto the next stage.
Step Two: Command Prompt Commands- Make sure you type these commands in one at a time and then press enter after each one. Most importantly make sure that you restart your computer once you have finish and then hopefully your Sidebar will be back up and running again.
Quote:
Pay attention to detail, make sure that you type in all the commands as listed below paying particular attention to commands with "" and %\ as these are very important. Any error messages you occur are because you have typed the wrong command or you have missed something out of the command.
Regsvr32 atl.dll [Press Enter]
You will now get a popup window which states that DLLRegisterServer in atl.dll succeeded. Click on OK to close
Regsvr32 "%ProgramFiles%\Windows Sidebar\sbdrop.dll" [Press Enter]
You will now get a second popup window which state that DLLRegisterServer in C:\Program Files\Windows Sidebar\sbdrop.dll succeeded. Click on OK to close
Regsvr32 "%ProgramFiles%\Windows Sidebar\wlsrvc.dll" [Press Enter]
You will now get a third popup window which states that DLLRegisterServer in C:\ProgramFiles\Windows Sidebar\wlsrvc.dll succeeded. Click on OK to close
What have I just done, well basically we have run what is called Windows Sidebar Repair - Reinstall which should reinstate Windows 7 Sidebar. I hope this works for you and you get your Windows Sidebar up and running again. If you get a large window with an error message then you have typed something incorrectly into Command Prompt. These commands are correct so there shouldn't be any error message at all.
REMEMBER TO RESTART YOUR COMPUTER
Simon