Can I sign in to both Skype apps on Windows 10 Anniversary Update at the same time?
It is not possible to sign in to both Skype Preview for Windows 10 and Skype for Windows Desktop at the same time. If you already had Skype for Windows Desktop installed, you will have both apps available since Skype Preview comes built-in to Windows 10 Anniversary Update. However, you can only be signed in to one or the other at a time.
For example, if you sign in to Skype Preview first, then sign in to Skype for Windows Desktop after, Skype Preview will sign out and close. The same will happen if you sign in to Skype for Windows Desktop first.
Also, if you shut down or reboot, you will still be signed in to the last app you used. For easier access to Skype Preview for Windows 10, you can Pin it to Start or Pin it to your taskbar.