ERROR: dbpath (\data\db\) does not exist.

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 ERROR: dbpath (\data\db\) does not exist.
 Create this directory or give existing directory in --dbpath.
 See http://dochub.mongodb.org/core/startingandstoppingmongo
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Create a directory for storing mongodb data

at the start specify it with

bin/mongod.exe --db_path my_data

Error: couldn't connect to server 127.0.0.1:27017 at src

C:\Jagat\tools\mongodb-win32-i386-2.4.9>bin\mongo.exe

MongoDB shell version: 2.4.9
connecting to: test
Fri Apr 04 20:27:30.640 Error: couldn't connect to server 127.0.0.1:27017 at src
/mongo/shell/mongo.js:145
exception: connect failed

C:\Jagat\tools\mongodb-win32-i386-2.4.9>bin\mongod.exe

You need to start mongod.exe first