Yes, you really have 2 ways to keep time up to date.
Have the samba server sync once a day, and have clients use net time in the login script, or have the samba server sync, and the 2k/xp clients use the w32time service to update.
Personally, we've always used the net time command off a samba server that has already synched time.
Matt J.
Please always take the time to backup any and all data before performing any actions suggested for ANY problem, regardless of how minor a change it might seem. Also test the backup to make sure it is intact.