Installing windows XP on newer machines presents a few challenges and this post aims to be a compilation of the challanges that were faced so far and (possible) solutions.

General Notes:

1) It is highly recommended to choose computers upto and including the Optiplex 780 (and equivalent) as the BIOS has legacy compatibility modes for the HDDs which makes installing XP much simpler.

2) Although this method will get you a working install of Windows XP, Device drivers are still hard to come by. Although basics functions of the display adapter should work with generic drivers, any advanced features will not work unless you get an old external dedicated graphics card with XP drivers. In the same way USB controllers, the sound card and networking WILL have issues (probably be unusable with the onboard controllers on newer machines.)

3) If you do decide to settle on a slightly older machine for XP, try and find one that was built for Windows 7 (no problems with xHCI) or for Windows 8 (without a BIOS update) as these will use the old EHCI standard(or have compatibility modes that disable xHCI in their BIOS as long as it hasnt been updated) instead of the newer xHCI standard for USB contollers. No working xHCI driver for XP could be found.

ACPI:

1) Most modern machines (and all desktops) will show up as non ACPI compliant for the XP installer due to the changing of ACPI standards and the BIOS lists not being updated.

...

• The newer Intel drivers are only meant to support the newest hardware on the (relatively) newer platforms so they are better optimized for these platforms and chipsets. Using an older version may yield an increase in performance if you notice the HDDs are particularly slow.
• The conventional (or legacy) Intel drivers with a single file DO NOT have support for TRIM operations (only applicable if you are using an SSD). The newer style drivers do not work on XP (though Windows 7 and up is supported along with limited functionality (there are known issues) with Vista)
• The Baytrail chipsets are not properly supported by Intel themselves so running anything that does not work out of the box on a Baytrail chipset may be a lengthy process of trial and error.
• In case you cannot find drivers for the specific system you are working on, it might be worth a try to unpack the supported version of the drivers(non-legacy) from both the files, and make an attempt to repackage and resign them in order to get them to a format recognizable by XP. A downgrade might also be possible if you know that the SCSI hasnt changed much (although in this case you would manually have to find the *.inf files with the device hardware Ids and add a line for the specific chipset that you are working on.) NOTE: Both these processes are only responsible for making the driver INSTALLABLE on the machine, they do not change the driver itself, so there is no guarantee that the repackaged and resigned drivers will work at all on the system. More information about using PkgSignTool can be found here https://msdn.microsoft.com/en-us/library/windows/hardware/dn789236(v=vs.85).aspx (For resigning drivers). You may also want to view this link: https://technet.microsoft.com/en-us/library/dd919238(v=ws.10).aspx for the process for signing new drivers.
• Instructions for importing the certificate for the WinRAID forum drivers (in case windows rejects them) can be found here http://www.win-raid.com/t1300f25-Tips-Discussion-Usage-of-quot-mod-signed-quot-Drivers.html

Further Support:

In case of need for further support (for both legacy and windows 7 drivers), the person who maintains the pages on the winRAID forums (Fernando) replies fairly promptly to both new posts on existing threads and messages (a couple of days) and should be able to help with any problems running legacy operating systems on newer machines (in terms of missing driver files). The information presented here is taken mainly from his guides and partly from various other sources on the web.