The latest version of Skype for Windows desktop includes some changes that have improved video calls, group video calls and screen sharing. Unfortunately, these changes mean that video calling and screen sharing won’t work on some older PCs.
If your computer doesn't have SSE2 support, you won't be able to use video calling and screen sharing. Most modern computers have SSE2 support (a processor instruction set introduced in 2001), but there are still some computers in use that won't be able to run all of the features of the latest version of Skype.
Unfortunately, there are no plans to include support for these older computers, but you can still use Skype on a variety of computers and mobile devices.
Learn more about the minimum requirements to run Skype on all supported devices.