Here are the instructions directly from the Gateway support site, this is where you go to get the AHCI drivers for your Laptop, and apparently this Laptop BIOS may indeed be locked into AHCI mode only.
Per the instructions at Gateway you have to use a USB floppy drive for the install
Information and Instructions about this download file
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File Description: Gateway(r) Notebook Computer Intel SATA Support Driver
Version: D00455-001-001
Operating System: Microsoft(r) Windows(r) XP Tablet OS
Part Number: D00455-001-001.exe
Date: 03/28/2006
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Table of Contents
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Overview
Identification
Installation
Removal
Troubleshooting
Reason for Update
Applicable Part Numbers
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Overview
This is the SATA hard drive driver for Gateway notebook computer models listed in the Applicable Part Numbers section below. This driver is needed during installation of a non-Gateway supplied operating system.
Identification
If you have a Gateway notebook computer listed in the Applicable Part Numbers section below and are installing an operating system other than what shipped with your Gateway computer, install this driver.
Installation
Note: Installation of this driver requires the use of a floppy disk drive. If your computer does not have an internal floppy disk drive, an external USB drive can be used instead.
Download the driver file to the desktop, and then perform the following steps.
1. If you have not already done so, locate and double-click the D00455-001-001.exe file that you downloaded from the Internet and execute the file. Files extract to the CCabs\D00455-001-001 folder on your hard drive.
2. Insert a blank floppy disk in the floppy disk drive.
3. In the CCabs\D00455-001-001 folder, double-click F6flpy32.exe.
4. Click OK to start the disk creation.
5. The disk creation dialog box closes when the disk is complete.
6. During the installation of Windows you will need install this SATA controller driver. Press the F6 key on your keyboard to install a third party controller driver.
7. The Windows installation program requires the use of a USB floppy disk drive and the floppy disk that was created above.
8. The Windows installation procedure attempts to load the drivers twice; once directly after the F6 selection, and a second time after the installation files copy to the hard drive.
9. Select the "- Intel(R)82801GBM SATA AHCI Controller Mobile ICH7M" option as listed.
Note: To find the required selection it may be necessary to scroll down even though there is no indication to scroll down.
Note: If you experience any recognition errors during the installation, please reference this Microsoft Knowledge Base article KB916196. This article explains which USB floppy drives are supported by the Windows installation process.
http://support.microsoft.com/kb/916196/en-us
Removal
Because the computer must have these SATA drivers when using a non-Gateway supplied operating system, these drivers are necessary and should not be removed.
Troubleshooting
If you have trouble installing the drivers, try creating another floppy disk, or use a USB floppy disk drive.
Reason for Update
This is the initial release of the driver.
Applicable Part Numbers
C-120 Series:
1014291R - Gateway C-120X
CX210 Series:
1008807 - Gateway CX210S
1008808 - Gateway CX210X
CX2700 Series:
1009036 - Gateway CX2724
1009063 - Gateway CX2720
1009089 - Gateway CX2724h
1013921R - Gateway CX2726
E-100M Series:
1008799 - Gateway E-100M
1008800 - Gateway E-100M G
1008973 - Gateway E-100M SB
E-155C Series:
1014294R - Gateway E-155C
1014292R - Gateway E-155C G
M255:
1008801 - Gateway M255-E
1008803 - Gateway M255-G
1008989 - Gateway M255-E SB
M285:
1008804 - Gateway M285-E
1008805 - Gateway M285-G
1008990 - Gateway M285-E SB
M465:
1008637 - Gateway M465-E
1008667 - Gateway M465-G
M685:
1008638 - Gateway M685-E
1008666 - Gateway M685-G
MP6000 Series:
1009092 - Gateway MP6954h
MP8000 Series:
1013924R - Gateway MP8708
1013975R - Gateway MP8708H
MX1000 Series:
1009046 - Gateway MX1025
1009097 - Gateway MX1023
1009098 - Gateway MX1023h
1013959R - Gateway MX1027
MX6000 Series:
1009028 - Gateway MX6214
1013916R - Gateway MX6216
1014062R - Gateway MX6433
5961 - Gateway MX6710
5962 - Gateway MX6750
6157 - Gateway MX6750H
6244 - Gateway MX6708
6245 - Gateway MX6708h
1008869 - Gateway MX6910H
1008963 - Gateway MX6951
1008962 - Gateway MX6951H
1009030 - Gateway MX6920
1009072 - Gateway MX6919
1009066 - Gateway MX6912
1009090 - Gateway MX6920h
1014033R - Gateway MX6956
1014028R - Gateway MX6955
1013928R - Gateway MX6930
1013918R - Gateway MX6931
1013973R - Gateway MX6930H
1013974R - Gateway MX6931H
1014065R - Gateway MX6957
1014072R - Gateway MX6958
1014061R - Gateway MX6959
1014068R - Gateway MX6960
1014080R - Gateway MX6961
1014112R - Gateway MX6961H
1014106R - Gateway MX6962
MX8000 Series:
1013955R - Gateway MX8710
2905895R - Gateway MX8710
1008827 - Gateway MX8750
NX100 Series:
1008798 - Gateway NX100X
NX200 Series:
1008794 - Gateway NX260X
NX500 Series:
1008796 - Gateway NX510S
1008797 - Gateway NX510X
1008644 - Gateway NX560X
1008652 - Gateway NX560XL
1009163 - Gateway NX570X
1014077R - Gateway NX570X
1009146 - Gateway NX570XL
1014078R - Gateway NX570XL
1014079R - Gateway NX570QS
NX800 Series:
1008645 - Gateway NX860X
1008647 - Gateway NX860XL
S-7000 Series:
1014293R - Gateway S-7125C
1008655 - Gateway S-7510N
1008648 - Gateway S-7710N
1014340R - Gateway S-7410M
Components:
4006186R
4006187R
4006197R
4006198R
4006199RYou can also try what is at this link to slipstream them into the XP CD
http://www.digitgeek.com/how-to-slip...rs-into-xp-cd/
Or perhaps, try to get a copy (or slipstream XP SP3 into the XP CD)
and then it should have SATA drivers in it already.