Slipstreaming and WGA

[#1]

I have a perfectly genuine copy of XP Pro OEM I bought a little while back for my main computer. When I install this the old fashioned way with the orignal disc then all the drivers, SP3 etc afterwards I have no problems with WGA. When I slipstreamed SP3 and all the drivers and created an unattended setup with Nlite suddenly the computer would not pass WGA valadition. Any ideas why? Is it just one or more specific options with the slipstreaming causing this that I could change?
This is a real pain because when I install the old fashioned way I have a real nightmare installing my 2 Nvidia cards without getting BSOD. The onboard audio on my Asus M3N78 is also a pain to get working after installation. When I slipstreamed the drivers it all worked perfectly by the time Windows was installed.

[#2]

The problem has just got stranger. After I installed and validated successfully I ran Magic jellybean keyfinder. The product key it returned was different to the one on the COA that I had inputted during installation?

[#3]

Issue resolved. I remade the slipstreamed disc using the product key I found on the computer with Magic Jellybean and not on the COA and it worked perfectly. Why did this product key change from that on the COA?
I thought maybe it happened when SP3 was installed but that never happened with Home Edition on my Laptop. Any ideas?

[#4]

There is a known problem where the early OEM keys failed validation when SP3 was slipstreamed (I had this one) and I wonder if SP3 changed the OEM key when it was installed to make it acceptable

[#5]

That does make sense. I am just happy that I now have a working slipstreamed disc for this computer and do not have to go through the nightmare of trying to get my two Nvidia cards working after install.

[#6]

With SP3 you dont need to give the serial during install so its like vista. Nlite is a bit confusing some times as it doesnt display all the scripts so if there was a script before you may not see it unless you view the source code. I have had problems when I have used a cd which has a script on it to start with as opposed to a basic MS one. Some OEM's have funny things going on.