Trouble with testboard install on same domain

[Booyakan]

Please need help.

I am trying to install a 2nd copy of my license on the same domain under a password protected folder for testing purposes.

I have my forums at example.com
and my 2nd install i want at example.com/testboard.

when I try to install at http://example.com/testboard/install/install.php

I receive the following error on the 2nd step of installation:

Action Required
Unexpected Text:

<?xml version="1.0" encoding="windows-1252"?>
<br />
<b>Fatal error</b>: Cannot redeclare class vb_xml_parser in <b>/home/example/public_html/includes/class_xml.php</b> on line <b>52</b><br />

[Lynne]

Did you try disabling your plugins via the config.php file?

[Booyakan]

I just ended up putting it on another domain and password protected it. Sorry if someone runs across this and needs an answer.