I have a situation where when i try to map network drive i get error : Access denied : Before opening file add it to trusted site and all. 

Strange part is it works for root site collection but not other site collection . Has any one seen this issue? I tried to follow this link

http://www.sharepointblogs.be/blogs/vandest/archive/2013/02/06/sharepoint-and-claims-map-network-drive-issue.aspx

, which make sense and checked setting but only thing i am amazed about is why does it work for root site collection but no anything else?

Hi Adit,

Please uncheck Enable Protected Mode for internet zone in the IE as:

1.Open IE -> Go to Internet Options
2.Select Security tab -> Select Internet Zone
3.UnCheck the box for Enable Protected Mode

Add your site collection into IE Trusted Sites.

And make sure the Web Client service is started on the client machine.

In addition, please make sure you are using Office 2013 32-bit.

Here is two similar articles, check if it is useful for you:

http://blogs.technet.com/b/sharepoint_made_easy/archive/2013/03/20/map-network-drive-webdav-with-sharepoint-online-o365.aspx

https://support.microsoft.com/en-us/kb/2616712?wa=wsignin1.0

Thanks,

Wendy