Are Wills valid if not notarized and witnessed if they are signed

I have a question about Probate and Executors and Wills... My uncle recently passed away and his sister my aunt was named Executor of his estate. She says the Probate process is underway, but says my uncle did not have a will, however I have a signed copy of his will, but it was not witnessed nor notarized, but drafted 3 years prior to his death. I and my sister were named in the will to received 5% of his estate, so, I wanted to know if the Will is valid or can the Executor simply not abide by his wishes.