Problem signing in

I've had several people contact me saying they had very difficult joining our forum. They were either told their email (or name) was already being used. Or, they were told the confirmation code was incorrect, even after they retyped it several times. They also said the confirmation code was difficult to read at times because the letter/number was in black and the background was black and therefore they couldn't read the letter/number.
Is there any way to disable that confirmation code so people trying to register did not have to use it?

AP > Users & Usergroups > Users > Users Options
Confirmation code:  No

Thank you.