how to install new copy of mybb 1.6.7?

[WINBOY]

This user has been denied support.

i want to remove current script mybb 1.6.7 due to so many problem in forum as if i currect one issue than second issue is created.

pls help how to install new script . as one is already running on server.

medishared.org

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I HAVE INSTALLED BUT How to remove all installed plugins from server.
i want fresh copy of forum.
please help.

in admin cp all plugins are there.