The Google Toolbar is installed in the folder
%ProgramFiles%\Google\Google Toolbar along with other folders and files - see report
Whereas the Toolbar notifier is found in its own sub folder located at
It has been noticed that some virus files are named after GoogleToolbarNotifier.exe
In the threatexpert analysis reports two such incidents are recorded, where a file with this name is found in the following locations
%AppData%\GoogleToolbarNotifier.exe - view report
%System%\googletoolbarnotifier.exe - view report
In both the cases the installer has been identified by antivirus programs as a virus.
Sometimes we download and run software from untrusted sources believing in the name of the files, we tend to think it to be a legitimate file.
So you should check the presence of this file on your computer and make sure you have a legitimate GoogleToolbarNotifier.exe on your computer and not a malicious virus file bearing the same name.