OSC Checkout/Account issue

Make checkout be available as "guest" checkout option so that a customer can make a purchase without registering an account. This is an OSCommerce store with some customizations. If someone did want to register an account, then just email and password would be required for future log-ins. We had this "nickname" function added and we want it removed, but without further problems (i.e., not required to register) for customers to make purchases. So, project is to remove anything that has to do with requiring a "Nickname" (was supposed to be called "username") upon checkout. Customer example explains: "Your "Delivery Information" page has a bug. I wanted to create an account and filled out the form but left "nickname" blank which issued an error and also removed the password fields. I filled in the Nickname and clicked the button again but I got an error on the password however since the password fields were not displayed, I couldn't re-enter it. The only way I could continue without starting all over again was to uncheck the "create an account" box."