XP Home Edition to Vista 32-bit Home Premium

I'm trying to use the Vista Back Up utility to back up my notebook files to
a Maxtor external hard drive installed on a desktop system running XP Home
Edition SP2...

I configured the maxtor drive to "shared on the network" read/write using
the share tab on the drive properties... Vista can see the drive as network
resource and can even copy files (notebook to maxtor and back), create
folders, etc.

When I try using the Vista Back Up utility, however, the wizard prompts for
a user ID and Password... I enter my XP user ID and Password... and it tells
me that it can't authenticate... I'm presuming there's some permission on
the drive that needs set, but XP Home Edition doesn't give access to
permissions the way XP Pro does...

Is there any way to by-pass or set the permissions on XP so the Vista Back
Up utility will work ? Cobian or some other back up utility would probably
work but I'd prefer just using Vista...

Any ideas folks ? thanks... m