Same thing happened to me Dana, but not with XP. I originally purchased two copies of Win 7 when it was first released. A Win Pro 64 bit OEM version that cost me about £60 ($90) and a full Win 7 64 bit Ultimate licence. The Ultimate licence was purchased via Amazon. When it arrived the 64 bit disc was missing, so I had to get a replacement.
Everything appeared fine until a year later when I had cause to format my main disc and reinstall the Ultimate version. When I tried to register it I wasn't able to. I ended up contacting Microsoft and was told I'd been sold a buisness licence (I was told by Microsoft that the activation code was good for around 50 computers). I paid £170 ($255) for the Ultimate version) and as a home user Microsoft said that I wasn't allowed to use the buisness edition (though for all intents and purposes the box the discs came in looked like a normal disc box with nothing saying it was a buisness edition.
They told me to contact the vendor, so I contacted Amazon and was told they were only the intermediary and was told to contact the actual company who sold it via Amazon. I tried contacting them several times for a period of around 6 months with no replies to my emails. In the mean time I'd reverted back to my OEM copy of Vista (which I didn't like as I had loads of problems using a lot of my software and games). After six months I got fed up and decided to look for a cheap version of Win 7. I found a site that was selling codes only (you could buy the discs as well, but I already had a disc and felt buying one for each computer was an unecessary expense). Oh yeah, I also purchased another online download of Win 7 Pro via my wifes college as they got a big discount for students, so thankfully I still had two copies of Win 7 Pro working and genuine, though the OEM version was tied to one of my older computers).
Anyway, I decided to purchase an activation code for the Ultimate version from a site I found, that sold Microsoft products (Win 7, Vista and Microsoft Office i.e. all variants of each; for example, Home, 32bit, 64bit, Professional, Ultimate etc) for only £45 (for the ultimate 64 bit version), which was really cheap. I actually needed another three copies to convert all of my other computers to Win 7, but decided only to buy one initially, as I was a little suspicious of the low price. However, on using the code it activated and passed Microsofts verification process, so I went ahead and purchased two more 64 bit Ultimate codes and a 64 bit Professional code (which was about £7 cheaper).
Everything seemed hunky dory for around 18 months but, about 4 months ago, all of the computers running these cheap codes suddenly got messages (that repeated every 20 minutes or so) saying I'd probably been the victim of software piracy (or something along those lines), plus automatic updates were suspended and a small permanent message appeared above the tray area saying This copy of windows is not genuine.
In total it's cost me around £340 ($510) and I've lost five copies of Win 7
That site was around for about a year before it disappeared, so I dread to think how many people got scammed.
I'd only purchased one copy of Win 8 on release (just to try it out - partly because they were selling copies for an amazingly low price). I did buy another one for my wifes laptop (but she hated win 8, so gave the copy to me for one of my other computers, then when the cut off date for the cheap copies passed (end of January I think), that's when I suddenly found my licences were rip offs. Thankfully I did find a site still selling the boxed versions of the Win 8 Pro versions at the introductory price of £39.99 (after the cut off date). They had all the authentification marks and looked identical to the one I purchased when Win 8 had been released. There was no way I was going to purchased codes only.
I just wish I'd purchased a back-up disc from the place I was scammed when I purchased the first code. I nearly did, but decided becasue I still had the boxed version I din't need it. I'm sure I'd have realized when I saw the copied discs as they cannot add the holographic strips on rip offs (I don't think they can?) at least not effectively. On close inspection copies ar ealways obvious.