by MacClipper (2007)
*** Please do NOT PM me with requests or questions, share them here so others can help out or benefit too, I do NOT answer such PMs so don't be offended if I don't. Kindly quote any reference to this guide with the whole url and do not reproduce any parts without my expressed permission. This guide is provided as is without any promises or compensation, thank you.
Aim - to accomplish the above without needing a complete re-installation or a repair installation of the OS.
For more advanced Windows PC users only.
MS KB922976 for Windows 7 or Windows Vista
eg. in W7 x64, original reg key values were both 3 instead of the 0 to be entered.
If you had previously installed Windows in IDE mode and now want to try out AHCI mode, you will need to jump through a few hoops cos merely switching to the AHCI mode in the BIOS will get you a nice shiny cryptic BSOD. This is also true for Windows Vista (yes, I tried) although Vista has built-in AHCI drivers which allow for a fresh Windows with AHCI install without the need for F6 floppy loading.
I prefer to install Windows with IDE mode and then switch over to AHCI once I have ensured that Windows is running as expected. imo, it is easier to troubleshoot under IDE mode cos in that mode, the Device Manager reflects the UDMA mode used wheareas there is no such indication under the AHCI mode. Encounters with ODD issues, bad SATA cables, failing PSUs (HD drops to PIO mode) have taught me this is the better way. Besides, I hate dealing with floppy disks especially since I haven't bought any for the longest time.
There are probably many ways to do so but I am going to elaborate on 2 methods which I have personally tried successfully on my Commando i965 & P5W DH Dlx i975 mobos.
Requirements
Intel SATA AHCI drivers in DOS format, the drivers are usually found on the mobo bundled disc but sometimes only as installers which have to be extracted in single file format (DOS format in Asus parlance).
I will attach the Commando bundled i965 AHCI drivers (both 32 bit x86 and 64 bit x64 versions) for reference so you will know roughly which files to look out for, of course you can try to use them too if you are running a i965 mobo. You can load these drivers on the HD itself or a thumbdrive or even from the bundled disc if it is available in DOS format - no floppies required. Just remember to find and use the appropriate ones for your particular mobo.
Let's make it simple (and prob. lengthy being step by step) and hencefoth I will refer to the harddisk containing your Windows OS as the HD. You may want to print out this guide so you can refer to it offline as well.
Method 1 (mobo with >1 SATA controllers)
If your mobo has an additional SATA controller eg. Jmicron (like my P5W DH Dlx), you are in luck cos this method mostly requires you to do a simple temporary cable swap.
1. Power down the PC
2. Swap the HD SATA cable from the Intel SATA controller to the Jmicron
3. Power on PC and enter the BIOS
a. Ensure the Jmicron is using IDE mode, next set the now Jmicron attached HD as the default boot disk.
b. Switch the Intel controller from IDE to SATA AHCI mode
c. Save BIOS settings and allow the PC to boot into Windows
4. Windows now auto-detects a new SATA AHCI controller has been found
5. Direct the Windows driver update wizard to the driver location and install, next Windows should ask to reboot.
6. Reboot and allow PC to go into Windows, check that the Intel SATA controllers are now in AHCI mode.
7. Power down and swap the HD SATA cable back from the Jmicron to the Intel controller.
8. Power up, enter BIOS and set the now Intel controller hosted HD as the default boot drive.
9. Save BIOS settings and reboot into Windows with AHCI now activated, enjoy.
...continued.