MongoDB needs a folder to store the database. Create a C:\data\db\
directory:
mkdir C:\data\db
and then start MongoDB:
C:\Program Files\MongoDB\Server\3.4\bin\mongod.exe
Sometimes C:\data\db
folder already exists due to previous installation. So if for this reason mongod.exe
does not work, you may delete all the contents from C:\data\db
folder and execute mongod.exe
again.