Permission denied for backup

Scenario:
-network setup as peer-to-peer (4 machines)
-backup done everyone night with win2000 machine
-full access rights from all points on network
-no problem with backup UNTIL
-notebook computer changed from WinXP Pro Fat32 notebook to WinXP Pro NTSF machine
-all permissions set to still enable full access from all points on network
-backup will not back notebook as it receives a permissions error
-notebook fully accessible from all machines manually for full access
?
This one is driving my boss nuts.
thanks in advance
have a nice day
dave