I'd be careful there Andrew - trading standards laws in the UK say that retailers aren't allowed to accept software back that has been opened.
I had great fun with that one when I worked in Staples - sooooo many people would buy some software and a box of CDs, come back a few days later and insist the software didn't work, and they wanted to exchange it. Then they'd come back a few days later again, etc. etc.
Great fun being allowed to tell them to piss off after a while.