upgrading to vb4 will it hurt seo

Okay my forum is in this order. http://forum.mydomain.com I have noticed that on vb4 it goes to forum.php when you click to goto the forum. I built all my back links to the url http://forum.mydomain.com so if I upgrade and its now http://forum.mydomain.com/forum.php will that hurt seo. ALso is there a way so when members want to goto the site...can you got directly to the forum or do you have to goto the content page?

You can rename forum.php to index.php and also make the change in the vBulletin settings to change that.

I would suggest waiting to upgrade your live site until vbseo 3.5 goes gold. We are planning a feature that is not yet included that will set your forum home as 'root' that is not available yet in the current RC.