Substitute MB in an OEM XP system?

Regarding replacement processor and MB:

You may want to post your previous PC specs just in case others would want to know what PC platform you're coming from (socket 775 of Intel, socket 939/AM2/AM2+ of AMD). Telling us your current PC specs would be helpful since it would make other members provide appropriate PC hardware suggestions that could still be compatible with your remaining/functional PC components (like audiocards, memory modules etc.) Sooner or later, you'd also have to decide whether to go the "Intel" path or "AMD" path.

Regarding the Windows XP:

I think Windows OS and even some VSTi (virtual instruments or software synths) keep track of your PC hardware as a whole in the form of a "system ID" or something similar. If you change your motherboard to a different brand and model (or perhaps make major hardware changes) you would be brought to a dialogue screen that makes you choose whether to proceed to Normal boot, Safe Mode etc. due to a recent hardware change (or a similar windows message) on boot up.

Your previous Windows XP installation resides in your PC's hard disk drive (the main "C:" partition/drive). It doesn't reside in your old motherboard.

Best thing you can do, assuming you already have a new MB and processor...and you can't get beyond the "recent hardware change detected" screen is to re-install Windows XP BUT only after you've backed-up your important files in your current hard disk drive...of course, there would also be better suggestions/alternatives from other members so you may have to wait until others provide their thoughts.

In the meantime, if you have important files (e.g. .wav files or precious recording takes of your current projects) in your hard disk drive that you need to access, you can try doing the ff:

1) Assuming you have another PC at home/work, you may want to remove your old HDD and connect it to an extra SATA port or IDE port (whichever is the case) of your other working PC. From there on, you may still be able to save to CD/DVD the files that you need to access.

2) Or if you have a laptop, you may still be able to save/copy or access your files by using an external 3.5" HDD USB-casing. Your old HDD would be recognized as an external storage device.

Jim and PathosLogos,
Thanks for your replies. I should have checked "add signature" to post the basics (e.g. Asus P5WD2 Premium, Pentium D 930, 2Gigs, many disks.). However, the technical data of how to do it and how to prepare are things I haven't come to address yet, though I have viewed microsoft's and others' instructions on how to try to do it without a reinstall.

The thing I am mainly concerned with is whether the OEM license leaves me room to substitute a newer MB/CPU combo.

Some other relevant technical data:
P.S. - Antec 550W (a modern MB/chipset would use less power than my existing)
Backups - I back up everything to redundant internal HD's.
Video card - current is AGP, I'd need a new one.
RAM - certainly prefer new
PCI slots - I'd need at least 2; or 3 if the new MB doesn't have onboard FW.
XP - required because of a video editing board that will never have Vista drivers.

Here are the words from MS that concern me:

Users who run a Microsoft Original Equipment Manufacturer (OEM) operating system may upgrade or replace most of the hardware components on the computer and still maintain the license for the original Microsoft OEM operating system software provided by the OEM, with the exception of an upgrade or a replacement of the motherboard. An upgrade or a replacement of the motherboard is considered to create a new personal computer. Therefore, Microsoft OEM operating system software cannot be transferred from another computer. If the motherboard is upgraded or replaced for reasons other than a defect then a new computer is created, and a new operating system license is required. If the motherboard is replaced because of a defect, the user does not need to acquire a new operating system license for the computer. The motherboard replacement must be the same make and model, or the same manufacturer’s replacement or equivalent, as defined by that manufacturer’s warranty. The reason for this licensing rule primarily relates to the end-user license agreement (EULA) and the support of the software covered by that EULA. The EULA is a set of usage rights granted to the end-user by the computer manufacturer. The EULA relates only to rights for that software as installed on that particular computer. The System Builder is required to support the software on that individual computer.

(Notes: Italics added by me; I am "the manufacturer"; my system is not defective just yet)