Skype recently released a new version of Skype for modern Windows. Below are new options for managing your availability:
Invisible: When you select to be invisible you can still get incoming messages and without others knowing you’re receiving them.
Sign out: With this release Skype brought back sign out. The app previously logged you in as soon as you booted Windows as it is connected to your Microsoft account.
Supported operating systems: Windows 8.1.
Here are instructions for the latest Skype features and a free upgrade to Windows 8.1 from Windows 8.0.