Solved ‘No mapping between account names and security IDs was done (0x80070534)

‘No mapping between account names and security IDs was done (0x80070534)

I have an Acer laptop running Vista Home Premium SP1 connected via a wireless network to a Desktop PC running Windows XP Professional SP3.

Attached to the Desktop is a Maxtor USB hard disk which is used for backup of the Desktop. I can read/write from the laptop from/to the Maxtor. When I use the Vista Backup and Control Centre on the laptop to establish backup on the Maxtor, I can browse to the folder on the Maxtor, but when I enter a username and password I get the following:

If I use an administrator username on the desktop pc I get:
‘No mapping between account names and security IDs was done (0x80070534). Please ensure that the username is valid’ … (it is!)

If I use a limited username I get :
‘You need full control permission for the network share. Make the user a co-owner, with Full Control. The network share cannot be on a computer running Windows XP Home. (0x8100002A)’ As I say above, I am using XP Professional SP3 on the Desktop Computer.

I can see several related threads to this problem, but none which are the same.
Can anyone help please?

For anyone else out there struggling with this one...
The answer to my prob was found (eventually) on the Microsoft Search site.
It is to a) display the Security Tab in the properties page for folders on the XP machine by unchecking the 'Simple Folder Sharing' in Folder Options in the Control Panel and b) to set the Folder properties/security tab for the folder to which you are backing up (on the XP machine) to 'Full Control'. Then it all works as it should. Easy when you know how!