HunronJoe, you clicked on the big blue banner that said '50% off', right? I just tried it and it DOES give you the 50% discount (i.e. total price is only $19.95). Give it a try now, it should give you a total of $19.95, NOT $39.90.
What I *think* happened is that you had previously visited the normal price purchase page, which put Winstep Xtreme on your shopping cart at the regular $39.90 price. I noticed that the shopping cart 'remembers' previous selections between visits. When you went back to that page, the shopping cart saw the same product and did not update the price/apply the discount code as it should have done.
My apologies, I'll warn BMT Micro (Winstep's payment processor) about what happened and will tell them to refund your order for the full $39.90 to make up for your inconvenience. Needless to say, the Winstep Xtreme license key you just purchased is yours to keep.
Thanks and once again my sincere apologies for what happened,