I suppose some questions..
Does the Backup Panel say Windows Backup has not been set up? If the explorer window is not the Starting Backup notice window, what window is it?
Since one of the first things it does is to check for possible backup locations, do you have hard drive space available for the backup?
Do you have an anti-virus running that might be interfering?
Any messages in the Event Viewer around the time you attempt to start the backup?
And just to check, you might run the System File Checker. Open an administrative command prompt and type the following command with Enter after.
SFC /scannow
Let it finish and make note if it mentions that some files cannot be repaired.