Thank you very much for responding, your answer has been helpful allready.
If a user messes up a paid registration form but has already created an account for themselves on the site, you shouldn't need to remove their user profile or ask them to come up with another profile to process a new registration. You should be able to go to your registration page (linked to from the Conference Management pages), click the Delete button next to their registration, and ask them to log in and redo the registration process from the scheduled conference home page.
I understand the need for having both user-accounts and conference-registrants, but it is a bit confusing for a lot of my registrants.
But the biggest problem is the need for me to delete a conference registration that has not been completed by payment. This particular situation is causing a lot of mail-correspondence since the registration process does not match how normal curious people act in real life. The process and it's consequences is simply not intuitive. A lot of people tend to start the registration process just to explore their options. Others just don't like PayPal. Others again stops the process for various reasons after they hit the "register"-button on the registration form. All cases leading me and them to a situation where external communication is needed. Explaining the issue involving registration beforehand only works as far as people reads the instructions, which many people don't.
I have been in contact with at least one third of all registrants about this very issue so far, which to me proves that something is not working as expected from the users point of view.
What I think would make the registration/payment process more streamlined is an option from the profile to pick up a registration-process that has not been completed by payment. Users needs to be able to pick up the registration at a later point themselves and maybe even make changes to which fee-option they would like to pay for.
Any way, thank you very much for responding to my problem here