Laptop arrived, how do I return it?

So after waiting 13 days for my laptop to come it's now here but.........don't think I want it!! I was over charged and it's taken as long for Dell to refund me the difference. I'm told that "experts" are on the case!! This really doesn't bode well for any potential issues under warranty does it? I mean if I'm getting little joy with a simple Paypal refund what's it going to be like to return a faulty machine!!?
So, if I don't get my refund soon I'll have to send it back, anyone else done this? It's killing me but the box is going to stay sealed ready to make it's journey back.