In this case manual migration required as there is no build-in way to migrate Sitebuilder sites from one server to another. Try to check following tread on this forum: http://forum.swsoft.com/showthread.php?t=46828. The same operation should be applied for 4.x Sitebuilder server.
Also, following KB article could be also useful in this case: http://kb.odin.com/en/5512