So far, I'm unable to duplicate your issue.
The text "error command line:" will be displayed by mongod.exe when the Boost::program_options parser throws an exception, and the rest of the line it displayed is the text for that exception. "
unrecognized line in ' ■l'" seems to show two errors; an unrecognized line and an inability to display the name of the file that contained the unrecognized line.
The config file is completely optional; it can be a convenience later if you want to change the settings of the Windows service because you can now change those settings in a standalone file instead of needing to edit the registry or reinstall the service. Since the config file is getting in your way, try installing the service without it.
Try the command line
C:\mongodb\bin\mongod --install --logpath C:\mongodb\log\mongo.log --logappend
You should see "all output going to: C:\mongodb\log\mongo.log".
Type out the log file to see if the installation was successful. If so, try starting the service:
net start MongoDB
If this doesn't work either, let us know what happens.