Before doing anything ensure you've backup all.
This must be used with care.
I asume you're using the default installation ( hypersonic ) if not you must do the change in your database
1- Stop jboss
2- Open the file server/default/data/hypersonic/okm_app ( if you're on windows with some utf-8 editor like ultraedit or gedit )
3- Look for something like "repository.home"
INSERT INTO OKM_CONFIG VALUES('repository.home','string','/home/jllort/software/jboss-4.2.3.GA-OpenKM/repository')
and change to your new repository path
4- Move the folder repository to your new path
5- Start jboss
We'll be waiting your feedback.