This is a very interesting thread, and one that pops up frequently in different boards.
Since I have inside information (used to work for a local computer store) I will share the scoop with you.
1) All the legal information you are basing your decisions on are coming straight from M$ (System builder site, EULA agreement, etc). You know this is a load of B$. M$ was sued by the US, and a lot of the states. Why? Illegal & anti-competitive tactics, including their licensing agreements.
2) If you want the TRUTH on what is legal and what is not, don't research in M$'s library. Look at THE LAW. To be more specific, look at copyright law. For copyright law to exist, you must acknowledge the FIRST SALE DOCTRINE. Without this, copyright law cannot exist. Here is a link to it
http://www.lib.ncsu.edu/scc/tutorial/basics2a.html
For more research, go to google and search for "FIRST SALE DOCTRINE"
FIRST SALE DOCTRINE
A distinction not always recognized is that ownership of the physical item, such as a book or a CD, is not the same as owning the copyright to the work embodied in that item. Under the first sale doctrine, ownership of a physical copy of a copyrighted work, like a book, permits lending the item, reselling the item, disposing of the item, burning the item, and so forth, but it does not permit copying the item in its entirety. That is because the transfer of the physical copy does not include transfer of the copyright to the work. A transfer or assignment of copyright must be signed and in writing to be valid [Sample Transfer Form].
In summary, once M$ has sold a physical copy of a product, I.E. Windows, they cannot restrict you from lending it (but not copying it), reselling it, etc unless you waive your rights. If you are a "Authorized" System Builder, you basically agree to all their terms and conditions, and are bound by their B$ rules AS A CIVIL AGREEMENT, NOT CRIMINAL. If you break their DISTRIBUTION rules, it is breach of contract, NOT copyright infringement.
If you buy a copy of Windows at a trade show, or from a local computer store, you obviously don't sign an agreement waiving your rights. You DO have a right to resell that software. If you upgrade your OS from 98 to 2000, you do have the right to sell your copy of 98. Just like when you upgrade your car, or your stereo, or anything else, you can sell your older one without restrictions.
Now here comes the tricky part - not everyone who sells M$ software is selling authentic stuff. This is where you need to make sure you know who's selling you the stuff. DONT buy off of EBAY (or any auction) because it's loaded with fraud, and don't buy from people spamming you with stupid emails. Buy from a local computer store YOU TRUST, or a website a friend recommends and has bought from. Everything I wrote above has nothing to do with counterfeit software. If you have something counterfeit (especially at your workplace) , trash it or burn it because that is a criminal violation and you don't want to be at the wrong end of a M$ beating stick.