Backup contacts:1)Install a file manager on your Bluestacks. Popular file managers are ES File Explorer, Astro File manager. I am using OI file manager from the marketplace.
2)Now you need to backup your contacts. Click on the settings button on the lower right of your Bluestacks screen.
3)You will now have the following screen, click on "Manage Contacts".
4)Click on "Show Menu" button on the lower left of the screen. Then click on "Import/Export".
5)Now click on "Export to SD Card". Then click "OK".
6)So now you have a .vcf file which contains all your Bluestacks contacts. You can use this file in other applications also to get your contacts back. Now go the home screen of Bluestacks, and open your file manager. Open the SD card in it, it should like this:
7)Now you need to copy that file to the shared folder of Bluestacks, so that you can access it in your operating system. So copy the file using the file manager and then paste it in your SD card's "bstfolder\BstSharedFolder". Now go to
"C:\ProgramData\BlueStacks\UserData\SharedFolder" in your computer and you should be having the .vcf file here. You can use it again when you need to get your contacts back. Follow the same procedure as done here, copy .vcf file in that shared folder, and then you can restore your contacts the same way you made a backup.
Backup WhatsApp data:1)Just copy the entire "Bluestacks" folder from "C:\ProgramData\" and back it up somewhere.
2)Afterwards when you reinstall bluestacks, just close bluestacks and all it related services from the task manager. Services with the "HD-" prefix are bluestacks services. Close them and then copy back that folder to "C:\ProgramData\". And you are done! You will again have all your apps, settings, whatsapp messages etc.