as far as to CentOS 4.4, a work-around solution for Optiplex 745 ICH8 controller is to add "all-generic-ide" as a kernel parameter during installation. The sata disk is recognised as "/dev/hda" , but the disk speed is actually normal, as the followings: hdparm -tT /dev/hda /dev/hda: Timing cached reads: 4776 MB in 2.00 seconds = 2388.36 MB/sec Timing buffered disk reads: 182 MB in 3.02 seconds = 60.29 MB/sec please dont't forget to add "all-generic-ide" again in grub.conf at the first boot. sles 10 (2.6.16.21-0.8-smp) works well on Optiplex 745. So I think a final solution is using RHEL 5 that we should be waiting at this moment. I ask everyone's pardon for my poor english.