Backup Manger for SharePoint 2.0

(my english isn't very good)

Hello,

I use this software for my MOSS 2007 Server. Obviously the Backup Manager uses the local Administrator account to access the websites at a web application. Is there a way to change this into an other account in another domain? Because I always have to add the local administrator to the group of websitecollection-administrators, otherwise it says "access denied". Also there is no way to restore a website to another webapplication, because I only can add the local administrator at website-level, not at the web-farm-level.
(Maybe this is more a Sharepoint-related question, but is it possible to add the local administrator permanently to the webfarm-administrators?).
Any Ideas?

Thanks.
spprakt