Hi Akshay,
you won't be able to run the notebook on your system - at least not in the strict sense. But there are other ways:
You can install the CDF player which will allow you to open and view the notebook. This is a good option if you just need access to the text and images. Also, if the notebook was written to run in the CDF player, you may find interactive controls to play with - but that will usually not be the case if the notebook was intended for use in Mathematica.
As an alternative, you can upload your notebook to the Wolfram Cloud, where you can get a free account and actually run the code in your notebook. The downside is that you will be limited in terms of memory and computation time, which means that computationally demanding notebooks may not run. But it's definitely worth a try.