If you have installed the VS 2010 SP1 in your machine and then if you try to install ASP.NET MVC 3 in your machine, the installation may fail.
If you check the installation log file you can get a detail that says Async CTP is not compatible with ASP.NET MVC 3 installation.
This blog describes a scenario on how to solve this, but unfortunately both methods did not help me. I was missing the 8BC707D3F85BD0B3F9C439FAC38EAE2E key in my registry.
I just removed the VS 2010 SP1 from the machine and installed the ASP.NET MVC 3 and reinstalled the VS 2010 SP1. Fortunately I have the SP1 offline installer with me. 
But the problem is when updating the VS 2010 to SP1 it does not give a choice to select the components we need.
Versatile Digital DNA 
I forgot to put the blog link mentioned in the post : http://chriskoenig.net/2011/04/13/visual-studio-async-ctp-vs-asp-net-mvc-3-tools-refresh/
By the way this helped me to have a look at the Async CTP. It’s really cool. In the near future I’ll publish an article on that.