Have you tried downloading Microsoft essentials from the Microsoft store? It tests for genuine Windows, and I don't believe it will disable anything if it isn't. It just won't allow you to download MSE. IF you can use and download MSE, then I would assume you pass all genuine test.
Also in the past I have run into WGA issues on Windows XP machines, it doesn't lock your desktop, it just has a really annoying constant prompt and blacks out your desktop to let you know you have a problem. You can still rollback via windows restore, and are able to use your computer while you get the license issue sorted out.