Convert a folder named "InstantChats" in PST to CSV

Hi all, 

I am currently working on a project to Convert a folder named "InstantChats" in PST to CSV. I have tried the approach mentioned on stack overflow 

http://stackoverflow.com/questions/577904/can-i-read-an-outlook-2003-2007-pst-file-in-c 

But i get the error at the following line 

MAPIFolder rootFolder = outlookNs.Stores[pstName].GetRootFolder(); 

Saying the object not found. 

Can some please help me with the code to do the conversion. I am ok with powershell or C# 

Thanks