Injecting AHCI drivers into a live Windows XP System

August 4, 2011 ∞

The best way to install AHCI drivers in Windows XP is to press F6 during Windows Setup, and reinstall Windows. That said, it is possible to inject the drivers into a live installation of Windows XP.

The problem is that Intel’s installer only lets you install the AHCI drivers if it can find the AHCI controller. However, if the controller is running in ATA mode, then the AHCI controller is hidden from Windows, and the install fails.

So before running the Intel installer, you need to bootstrap the AHCI driver into Windows XP.

Before following these instructions, make your backups are up-to-date.

Get the correct AHCI drivers from Intel.
Extract the installer using uniextract.
Copy Drivers\x32\iaStor.sys to C:\Windows\System32\drivers.
Open Drivers\x32\TXTSETUP.OEM.

Scroll down to the [Config.iaStor] section. This section is used to create the iaStor service. First, create a new key in the registry. Then use the information in the [Config.iaStor] section to create the relevant values.

For example, if the [config.iaStor] section looks like this:

[Config.iaStor]
value = "", tag, REG_DWORD, 1b
value = "", ErrorControl, REG_DWORD, 1
value = "", Group, REG_SZ, "SCSI Miniport"
value = "", Start, REG_DWORD, 0
value = "", Type, REG_DWORD, 1

… then you need to create a .reg file with the following contents:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\iaStor]
"tag"=dword:0000001b
"ErrorControl"=dword:00000001
"Group"="SCSI miniport"
"Start"=dword:00000000
"Type"=dword:00000001

Add another entry for the driver to the service definition:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\iaStor]
"ImagePath"="system32\\drivers\\iaStor.sys"

This tells Windows where to find the driver.

Create and initialise the Enum key:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\iaStor\Enum]
"Count"=dword:00000000
"NextInstance"=dword:00000000

I’m not sure what this key does, but Windows appears to need it.

Now for the tricky part. You need to add all the device instance IDs for the AHCI controllers to the Critical Device Database.

In the TXTSETUP.OEM file, there are a whole heap of sections which look like this:
```
[HardwareIds.scsi.iaAHCI_ESB2]
id = "PCI\VEN_8086&DEV_2681&CC_0106","iaStor"
```
For EVERY one of those lines, create a new key in the CriticalDeviceDatabase. The name of the key will be the first string, except converted to lowercase, and the backslash replaced with a hash. Inside each key, create the Service and ClassGUID items:
```
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\CriticalDeviceDatabase\pci#ven_8086&dev_282a&cc_0104]
"Service"="iaStor"
"ClassGUID"="{4D36E96A-E325-11CE-BFC1-08002BE10318}"
```
The Service is the second string in the id = ... line. The ClassGUID value is a bit of magic which tells Windows what kind of device it is (in this case, a storage device).
Windows should now have enough information in the hardware database to be able to boot from an AHCI controller. Reboot into the BIOS and set the disk controller to ACHI mode.
Boot into Windows.

If Windows boots, congratulations! You can now run the full Intel installer to complete the device installation. If there ware a problem, double‑check the instructions above. And if Windows bluescreens, then it should work fine after disabling AHCI mode in the BIOS.

Good luck!

Bennett Perkins

bennettp123