Some CDs are marked for business use, (builders) there are many options offered, (or used to be) by MS. My 1st comp was an IBM from my parents when they up'd to a gateway in late 90s, win 95, no CD, there was supposed to be a recovery disk but they had no idea where it was. In early 98 bought a win 98 up grade disk and loaded it. Months later said disk died, (3 gb disk ... WOW). I bought a new disk and tried to load it, it wouldn't, I called MS, (pre internet our house) explained the problem and asked why I was having an issue. I was told that the upgrade version is the full version of windows plus 1 extra file, this file searches for an existing copy of windows, if it doesn't find one, it closes. They gave me a new key and the CD worked. Fall 98 got internet
A couple yrs later my parents on their 3rd or 4th comp asked me if I wanted them. I took them figuring I could add a 2nd comp in the kids room. I scavenged and combined parts from both to build a slightly faster pile but the CD that they got from the builder wouldn't work. I was told by a couple people, apparently (builder) had license on the key code to use it on builds but it was no longer valid, for (whatever reason). So I cloned the win 98 "C" from my pile, (old disk copy) and stuck it into the kids pile, (99/00) prior to MS's later pirating thingy, (multiple comp licensing?) and said to hell with it. Later in 00 I added the internet to the kids room to free up the living room pile, (school junk) and never heard a peep from MS.
Never bite the hand that looks dirty!
The more you know the more you're worth