I do not want Microsoft Messaging. I want Yahoo Messenger. How do I get it to download and turn Microsoft Messaging off?

I upgraded to windows 8 and since then several of my contacts have become blocked, and I don't know how to unblock them It say's they are not on messenger itself, but places like Merged Skype/Messaging app on windows 8 say that I can not message them because they are blocked.

I upgraded to windows 8 and since then several of my contacts have become blocked, and I don't know how to unblock them It say's they are not on messenger itself, but places like Merged Skype/Messaging app on windows 8 say that I can not message them because they are blocked.

I have been using  W7 for 8months or so without problem. My log in has for many years been @hotmail.co.uk.Last 2 weeks I have not been able to access  Instant Messaging  site as I am constantly told that I need to connect to internet when I am already connected through Google Chrome.I note also that my IM and windows  access log on has changed to hotmail.com. I have overcome the problem on access to windows live log in but not IM service    Help please .