This is a VBulletin tips to owners who used VBSEO url rewriting add-on but later would like to uninstall it for any reasons. After using VBSEO for quite sometime, and your forum URL already indexed by search engines, uninstalling VBSEO will make you loosing the visitors.
Here is what I did, for example your VBSEO is something like this:
Uninstalling VBSEO will make the URL return to default:
But unfortunately this translation from old URL to new URL is not automatic. Thanks to .htaccess, you can add this little line in that file and put it in your web root /.
RewriteRule ^forum(.*)/([0-9]+)(.*).html$ /forum/showthread.php?t=$2 [L,R=301]