Win XP Backup Utility

I recently installed a Buffalo Technologies NAS Drive on
my WIN-XP system. It appears to be running an imbedded
version of NT 4.9. The problem is, when using the Windows
backup utility, the archive bit for files on this drive do
not get cleared, thus making incremental backups useless.
All files become candidate for backup in incremental mode
because thats what the utility uses to select files to
backup.

Does anyone konw of a way to correct this? i.e. set/clear
the archive bit as appropriate.

Alternativly, is there a hidden option somewhere to
specify the modification date as a parameter to the backup
utility? This feature appears to have been removed from
the utility at some point. I would be happy if I could
specify "backup files modified since mm/dd/yyyy"

Hopefully someone knows a good answer!
thx