The problem was caused by the McAfee Antivirus, see this benchmark with a "clean" windows XP SP2 instalation, using AHCI:
Very good firmware upgrade!!!
3.AAM is essencial for those drives.
I can't read SMART with AHCI mode, HD TUne and HD Scan dont get the data from HD. Is there a way to read SMART when using the HD in AHCI mode???
Thanks