MongoDB is extremely easy to Install and start running. Just Install the file unzip it in preferably C drive.
Now open command prompt and type the following commands.
C:\> mkdir \data
This is where it basically stores the data. Now just go to the folder where you have unzipped MongoDB and then in the Bin Folder start Mongod(server) and Mongo(Client).
Your MongoDB has started and is up and running.
For more go to (http://www.mongodb.org/display/DOCS/Tutorial)