My Dell Vostro 1520 laptop (~3 years old) came with Windows 7 Pro and AHCI enabled (NCQ was a feature I was looking for at the time - it has to be supported by both chipset and HDD), and the recent upgrade to Windows 8 Pro went smoothly in AHCI mode (I remember what pain it was to change my Windows 7 work laptop a couple years back from legacy to AHCI mode post-install).
With all that work cut out for me, all I had to do is install Intel Rapid Storage Technology (RST) package (console and driver) - latest version available 184.108.40.2063.
Dell Vostro 1520
Intel ICH9M (Intel G45 Express chipset)
Seagate ST9320423ASG HDD
Windows 8 Pro x64
- Before: Windows 8 standard
- After: Intel RST driver