Can I return a replacement netbook to Amazon that was not the correct replacement after 30 days for refund?

I ordered a Windows 7 Starter ASUS netbook as a Xmas gift, but received one with XP Home installed. I returned it immediately & received a replacement that still had XP Home. I was told to start from scratch, order a new one & return the replacement. Personal cirstances prevented me from returning the replacement within 30 days & I still want to return it. It is sealed...never opened. Does anyone know? I'm hoping for some ideas before I call. I was still able to print the replacement authorization & shipping label, but don't want to return it & end up receiving a partial refund or something. Thanks for your help/thoughts!