I suggest you fix your registration page. A friend of mine can not create his own account. It says he did not enter the correct code, and I saw that he did with my own two eye balls!
I just resgistered a new test user. It works fine. Please tell your friend to ensure he is using the correct capitalisation; C is not the same as c. If he isnt sure what letter he is looking at, refreshing the page will load a new code to try.
Let us know how he gets on.