Installing Mongodb in Windows machine is some tricky, just follow the below Steps orderly.

Step 1:
         Download the Mongodb from the LINK
Download Mongo DB
Step 2:
        Right Click and install the mongo DB as Shown in the pic below

Double click to install mongo DB
Step 3:
          Click on Next and then Proceed

Click on Next

Step 4:
           Choose the setup type as Complete and click on Next

select Complete option

Step 5:
          Your installation will progress as Shown below

installation in Progress
Step 6:
           Your installation will complete. Now click on Finish

Click on Finish
Step 7:
        Your installed Mongo DB will be in the path  C:\Program Files\MongoDB\Server\3.0\bin ”

installed Path
Step 8:
            Go to My computer -> Right Click ->  Properties as Shown below

My computer Properties
Step 9:
          Click on Advanced System Settings

Advanced System Settings
Step 10:
               Then click on Environment Variables 

Environment variables
Step 11:
        Select the “path” in System variables section and click on Edit option 

Edit the Path variable
Step 12:
          Copy the installed Mongo DB path as Shown below

Copy the path
Step 13:
         Paste the path in the “path variable value” that had selected in above step

*** [Don’t remove the existing value in it, just append the copied text at the end of the existing value. Paste after the semicolon]

Adding the path value
Step 14:
          And click on “OK” of all the opened windows

Step 15:
  •  Open command prompt by typing “cmd” in the run
  •  And then enter the below commands as it is

     Type md   \data

    Next type md    \data\db    
   Next type mongod

Your cmd prompt should look as below

Your installation of MONGO DB is complete.... you can use it now.