maximum lenght domain name

I've got a small problem. I client of mine, registered a domainname with us which contains 28 characters (without www). The problem is, is that he can only create usernames, with a maximum of 3 characters. ISPConfig doesn't allow more characters with this domainname. I know the domainname is quite big, but why am i to question the domainname, if he pais me for it.
So is it possible to extend the character lenght somewhere?

 

I think the posts below will help:

http://www.howtoforge.com/forums/showthread.php?t=12308

http://www.howtoforge.com/forums/showthread.php?t=11316

 

I forgot to tell you that I already changed the database username to 64 characters, but it's ISPConfig that doesn't allow characters longer than 32 (i think).
I changed in the Form Designer the form username the width to 30 and the maximum length to 64. This doesn't work.

EDIT:
I run Debian Etch 4.0 and it doesn't support usernames longer than 32 characters...... so there's nothing to do about it.

 

In Ubuntu 8.0.4 /etc/adduser.conf add:

## Add username > 32 char
NAME_REGEX="[a-z0-9]*$"



works fine

 

which file contains the form?

soho I have a question:
The Form Designer that you was changed is in the file isp_username.plugin.php
?
Best regards.

 

Indeed, this is the file and the line should be changed is the 84:
$out_user = $user_prefix.'<input type="text" name="plugin[user]" size="'.$len_textbox.'" maxlength="'.(64 - strlen($user_prefix)).'" class="text">';

May also change the size of the box on the next line:
$len_textbox = ((30 - strlen($user_prefix)) < 10)? 10: 29 - strlen($user_prefix);