Argos Laptop purchased just over two weeks ago want to return it?

I believe their 30-day money back guarantee applies only if something is defective. And unfortunately you've opened it and used it. You can say you've done little to nothing with it, but there's no way to be sure on their end -- you could have planted spyware, changed out parts, etc. They certainly can't sell it again the same way as a new one. You're likely stuck with it and can try to sell it elsewhere yourself, but it's unlikely you can return it.