Enabling AHCI enables NCQ (Native command queuing) and faster multi-tasking response. See this article describing why you should use AHCI instead.
So when you do get a chance in do a fresh install of Windows 7, check your BIOS to make sure that AHCI is enabled to save yourself the headache of having to play around with it later.
Manually Enabling AHCI
This is for people who forget to enable AHCI on their Windows 7 install and want to enable it after to improve hard drive performance.
If you enable AHCI in bios after installing your Windows 7 in IDE mode, it wont boot. Since Windows 7 already has the drivers built in, you have tell it to enable the drivers since they will be off if you installed in IDE mode.
These are values exported from directly from my registry. Windows 7 RTM 64 bit only. Copy into text file and import, then restart computer and enable AHCI in BIOS before Windows boots. This is supposed to enable the built in Windows 7 AHCI driver.
To modify this for a 32 bit install, change the value of “DriverPackageID” to “mshdc.inf_x86_neutral_3f3676f4c0e7d884”
BELOW IS THE CONTENTS OF THE EXPORTED REG FILE:
Windows Registry Editor Version 5.00