actually guys, i found the extra speed very noticeable when i switched ICH9R sata ports from IDE mode to AHCI mode with a NCQ capable hdd.

when installing xp pro, the sata ports were in ide mode. after installing xp, i installed the ICH9R AHCI drivers and switched to AHCI mode in BIOS. intel's matrix storage manager now shows the hdd working under the ICH9R AHCI controller.

on an average of 5 start-ups:
sata ports in ide mode: 16secs to desktop (after mobo POST)
sata ports in AHCI mode: 12secs to desktop (after mobo post)

keep in mind that this is a almost 'clean' xp pro sp2 installation, only mobo chipset drivers, audio drivers & atio graphic drivers installed.
i imagine that after installing antivirus/firewall and all other necessary software, the difference could be even bigger, don't u think?

asus P5KR (Intel P35 & ICH9R)
Q6600
seagate ST3250620AS 250gb 16mb cache sata2 NCQ able