You dont need side bar anymore, rightclick anywhere on desktop and goto gadgets, Add the ones you want, put them where you want (side, top, anywhere) and thats your gadgets as they were in vista,
Or try
How to Enable Sidebar & Desktop Gadget with Disable/Turned Off UAC in windows 7
1. Click on start and type regedit on search bar
2. Now navigate to follow registry key in left pan of registry editor
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Sidebar\Settings
3. Right Click in right pan of registry editor to Create A New DWORD(32 Bit Value) with name “AllowElevatedProcess” and set value as “1”.
4. Now close registry editor
5. Right click on desktop and add desktop gadgets to confirm Desktop gadget and sidebar working properly
http://www.winsupersite.com/win7/ff_gadgets.asp
What's changed since Windows Vista?
So. What has changed since Windows Vista? Microsoft has made the following changes to Windows Gadgets in Windows 7:
No more (visible) Sidebar. The Windows Sidebar UI is now removed in Windows 7 because so few people left it enabled even though it was turned on by default. The people have spoken. Note, however, that the Sidebar executable, sidebar.exe, is still running in the background when you have any gadgets displayed. Yep, it's that lame.