Here is a concise breakdown of the situation regarding : The Evolution of Skype on Windows 7
If you are still using a Windows 7 machine and need to communicate:
While Windows 7 itself is no longer supported by Microsoft, the final "modern" version of Skype (version 8) was designed to run on Windows 7 SP1. However, even that support is fading as web standards evolve. How to Get Skype Working Today