Ok, can you get into your board at all? If not then you'll need something like phpmyadmin to run a few sql queries that are below:

ALTER TABLE w3t_Users
ADD U_LoginName VARCHAR(64) NOT NULL,
ADD INDEX Login_ndx (U_LoginName),
ADD U_AdminEmails VARCHAR(3) DEFAULT 'On',
ADD U_EmailFormat VARCHAR(10) DEFAULT 'plaintext'


UPDATE w3t_Users SET U_LoginName = U_Username


ALTER TABLE w3t_Posts CHANGE B_ParentUser B_ParentUser VARCHAR(64) NOT NULL,
CHANGE B_Username B_Username VARCHAR(64) NOT NULL,
CHANGE B_Icon B_Icon VARCHAR(30) NOT NULL

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Rick Baker
UBBThreads developer