If your Save option in the Windows Snipping Tool is not working have a look at the Registry Setting for My Pictures under Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders

If it is pointing to an invalid location, for example you have previously modified a drive letter, you may need to update this to the correct location. Just make sure you restart the Snipping Tool when you have made the Registry Correction. Please note, any modifications you make to the Windows Registry are made at your own risk.