I didn't realize that. I wonder why you can do it for a retail
With retail you can move the op system from box to box and MS doesn't care as long as the key is only active on one box or motherboard at a time. MS's only concern is that you are not trying to use that key on multiple computers at the same time.
but the OEM boxes you can't. Very interesting and thank you for that new bit of knowledge.
With OEM the license is for the entire unit (the box). Specifically it is tied to the motherboard and IIRR the EULA does not allow the MB to be changed from anything beyond the exact OEM replacement. You can change drives, video cards, CPUs and just about anything else except the motherboard in an OEM system and MS won't care. Where you might run into a problem is when you change the MB to something different and use the OEM key (or COA) from the original system.
Google the procedures on OEM re-installations. There are a lot of articles that explain the legalese of the OEM EULA better than I can and ways to deal with it legitimately (activations and WGA authentication) as far as MS is concerned.
Side Note: While I would not do this again nor recommend it professionally, on a personal level I have moved OEM op systems around on a couple of different machines in the past.
In the first instance I reworked an HP system with a dead HDD and a seriously ugly case. Put it in a new case and re-installed the OEM software using the key from the HP box. Took the COA sticker off the HP box and put it inside the new case. Essentially nothing changed except the HDD, the case and the video card, but the MB was still the same as the original system. It activated and WGA authenticated with no problems.
Second instance I had an eMachines T series that had a dead Trigem P4 MB in it. It sat on the storage rack for about six months before I got a PC Chips A33G MB with an Athlon 64 x2 CPU for it. Put that MB in the original eMachines case, re-installed the OEM XP, used the key on the box and it also activated and WGA authenticated with no problem.
Two different situations granted, but in either case did I violate the OEM EULA?
In the first with HP, yes I probably did because I moved the COA sticker to the new case even though the essential hardware didn't change. This system has since been retired and is no longer active.
In the second case it is a little more of a gray area since the MB change went back into the original case and the system had sat inactive for 6 months prior to the change. This system is still in active use.
I'm pretty sure that if Microsoft
really wanted to make an issue of it they might find that the changes were a violation of the OEM EULA. But both machines ran flawlessly and as far as WGA was concerned were fully authenticated and the keys were legitimately purchased or transferred to me.
Point being that it can be done if you follow the proper procedures.