You’ll have to forgive me here folks, this isn't a very constructive screencast. I was frustrated at the crappy checkout process for a software product I was trying, so I thought I'd screencast it as a lesson to us all on how not to design a checkout. It was confusing, frustrating, error-prone, and make me feel unsafe about even going through with the transaction. If you are designing a site to sell something online, nothing is more important to your…