it think that the Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group works great, all my page in google dont point anything to vBulletin, also change the pówered by vbulletin in the arhive/index.php in that file change it, i search vbulletin site:my_site.com and doesn´t point anything this is a good disquise,
thanks to GYSN for that idea, also use a keygen version to avoid host reporting to vbulletin, they (your host) will look at all your files searching vb license if they find it you´re ok, i´m runnig vb software since 2002 and they don´t have busted me, only remove all that stuff og vbulletin just try this search using Google
http://www.google.com/search?q=vbulletin
you will find a lot of vb webs my site is now powered by phpbb