If you are using windows 7 then there is a simple step to copy your whatsap data to your pc..
1. Go to C drive
2. Go to users
3. you can see the all user open it
4. there are 2 folder you can see related BlueStack and BlueStacksetup Open BlueStack
5. In this folder you can see Shared Folder. Create it shortcut to your Desktop
6. then Install File Manger, open it at
startup window you can see bstfolder open it and there you c BstSharedFolder..
7. Copy any data like, Whatsapp videos and paste it to BstSharedFolder. then open Shared Folder as you created shortcut on your desktop..
and you can access your whole BlueStack data using this step..
Try it ...