What should i do with my pc computer?

I have a computer that don't work good it has a lot of virus in it and it sucks so I want to clean it and fix so I could send it to my sister in guatemala what should I do with it what do I have to do? Will it work in guatemala that's where she lives would it work over there? I want to know what I gotta do first I don't know much about computers is an hp is a good computer is like a 2008 model help!