Most obscure/upvoted answer will get the answer vote!
Most Unix and Unix-like systems have a "traditional history" that is passed down with each generation, so that newcomers can see and understand some of the more esoteric portions of the system. What can the long-time Windows admins out there contribute as to the "Legendry" of Windows, as far as esoteric knowledge that new admins should be exposed to?
There is a widespread urban legend in the Windows community that Dave Cutler chose the name "Windows NT" (WNT) because if you subtract one from each letter you get VMS, which is the operating system that Dave Cutler worked on before he came to Microsoft.
However, that is not true. Neither did Cutler choose the name (it more or less emerged by accident) nor was the name WNT (it was, in fact, "NT OS/2", because at that time, the idea was still to build the next generation of OS/2 – Windows wasn't even in the picture). NT also doesn't stand for "New Technology".
Dave Cutler was hired by Microsoft to build a next-generation operating system for the PC. At that time, Microsoft's most modern OS was OS/2, built jointly by IBM and MS. And so, to MS, "next-generation" naturally meant a new version of OS/2. (Windows was just seen as a GUI for DOS, that would soon be replaced by a real OS.)
At DEC, Dave Cutler had worked on VMS. One of the problems with VMS was that a lot of it was written in assembly, and that it was fairly monolithic. Both meant that it was somewhat hard to port to other platforms. When he was tasked to write a successor to VMS, he changed all of that; while he liked the abstractions and style of VMS, he didn't like the implementation: he wanted to write it in a highly modular style, and he wanted to do it in C – basically a cleaned up and modernized re-implmentation of VMS. DEC soon lost interest in his project, and effectively mobbed him out of the company, which is how he ended up at Microsoft, where he was able to implement his ideas. (Which is why NT looks so similar to VMS: it's essentially the version of VMS Cutler always wanted to write but DEC didn't allow him to.)
So, Cutler was writing a new version of OS/2. At that time, it was not at all clear, what exactly a "PC" was and that the i386 would win out. Intel was experimenting with RISC processors, Microsoft was experimenting with MIPS processors, IBM was doing the PS/2 and later also the PowerPC, DEC's Alpha was around the corner. Building an operating system for only one of those platforms would have been a huge and dangerous gamble. So, the new OS/2 would have to be highly portable. In order to ensure maximum portability, Cutler tried to find the strangest, most PC-unlike architecture possible. And he found the Intel i860. The i860 was 64 Bit, the i386 32 Bit. The i860 had plenty of registers (32), the i386 only 8. The i860 is RISC, the i386 CISC. The i860 has a VLIW architecture. It had a SIMD unit on the chip (that would later become the inspiration for the MMX SIMD instructions on the Pentium MMX). It exposed its pipeline to the software, so that all the scheduling decisions that the i386 makes on the chip, would have to be made by the compiler (this was the inspiration for the EPIC architecture of the Itanium). And it had one of the strangest memory models ever.
In short, it was the perfect target for a highly portable OS: if you developed and tested on the i860, you could port it almost anywhere. So, that's what Cutler did.
There were two versions of the i860: a cheaper, simpler one called the XR and a faster one for SMP machines called the XP. Except MS was working with early prototypes and the marketing names hadn't been chosen yet, so they were simply known by their Intel codenames: N10 and N11.
The operating system that Cutler was working on, was codenamed Portasys, because of its portability. However, internally they didn't call it that: they were building it for the N10, and they were building a version of OS/2, so in conversations they simply called it "OS/2 for N-Ten" or "N-Ten OS/2", and because programmers are lazy, that quickly got shortened to "NT OS/2".
Then, two things happened: MS hadn't actually bothered to tell IBM that they were building their own version of OS/2. When IBM became aware of the fact that the new OS/2 was actually quite different from the old one, IBM and MS had a falling out and the joint development of OS/2 ended.
The second thing that happened was that Windows 3.0 took off beyond everybody's wildest dreams.
That's when MS changed directions 180°. And now the modular design of NT OS/2 came in quite handy.
In NT, there is a clear distinction between the kernel and what is called a "personality". Usually, the kernel's job is to abstract the hardware and present an abstraction to userland. In NT, these responsibilities are split: the kernel abstracts, and the personality presents the abstraction to the userland. Well, actually, the personality does not present the abstraction, it presents an abstraction; there can be multiple personalities.
At this point in our story, NT looked like this: there was the NT kernel, on top of the NT kernel was the OS/2 personality, and on top of that was the OS/2 Presentation Manager (GUI). The filesystem was HPFS. Because of the personality abstraction and the ability to run multiple personalities at the same time, it was now very easy to keep the system running while at the same time adding a Windows personality. Once the Windows personality was complete, Presentation Manager running on top of OS/2 was replaced with the Windows UI running on top of Windows. HPFS was renamed to NTFS and some tweaks were made.
And then some marketing guy somewhere decided that that "NT" moniker was actually kinda cool, but the "OS/2" thing had to be replaced with "Windows" and it sounds better the other way around ("Windows NT" instead of "NT Windows"). And when he was asking what NT stood for, they told him that it didn't actually make any sense because they weren't doing an i860 version any more, and so he retroactively created the backronym "New Technology".
That's how it became WNT. And, as you can see the letters "N" and "T" were chosen by chosen by Intel, the letter "W" was chosen by fate and the ordering of the three letters was chosen by some marketing guy, so there is simply no way that anyone could have consciously chosen them in relation to VMS.
And, by the way: Arthur C. Clarke has always said that he never thought about "IBM" either, when he came up with the name "HAL". In fact, he said that if he had recognized that relationship he would have changed HAL's name out of respect to IBM with which he had very good working relationship.
I don't have any stories personally, but I can point to some:
I always thought the fact that you could change NT Workstation 3.51 to NT Server with a registry change was pretty cool. And says everything about Microsoft's market segementation strategies.
How about Osterman's explanation of ctrl-alt-delete in his post Why is Control-Alt-Delete the secure attention sequence (SAS)?
Windows has a legacy that dates back to before the first versions of MS-DOS to CP/M, including:
(*) Trivia: DOS COM files get loaded into memory at 0x0100:0000 (segment/offset); CP/M COM files got loaded into memory at 0x0100
Correction 9 July: CP/M COM files got loaded into memory at the absolute address 0x0100. DOS COM files get loaded at offset 0x0100 in the next available segment. (Thanks to Euro Micelli).
The (In?)famous 49.7 day stability bug in Windows 95. Under certain circumstances, you'd want to reboot your machine every 49 days to avoid the bug from tripping up parts of your system. No, it didn't force a shutdown or anything like that, it just produced strange results...
Some quick links found...
CNET: Windows may crash after 49.7 days
MSDN: System.Timers.Timer and System.Threading.Timer bug after 49.7 days!
The Joel on Software Discussion Group: The Windows 49.7 days shutdown bug
A couple bits of trivia:
Dave Cutler was one of the designers of DEC's VMS operating system, and then the chief architect of Win NT at Microsoft. Just as HAL (from 2001: A Space Odyssey) was said to be one letter before IBM, WNT (Windows New Technology) is one letter after VMS.
We all know what NT stands for, and there was that annoying line on the startup screen of Windows 2000 that said "Built with NT Technology," i.e. with New Technology Technology.
This isn't so much Windows trivia, but it's also DEC-related. DLT and LTO tape formats are descended from Digital's infamous TK-50 tape cartridges. Infamous, because TK was widely said to stand for "Time Killer." The later TK-70s were a bit better, but not much.
I remember a fight with Digital Equipment way back in the day trying to get the Alpha NT linker to work to link Pro/Engineer on NT 3.5. This particular release of Pro/E broke the 32MB executable limit (wow, remember when that was a big deal)? Needless to say, I tell myself today that DEC's refusal to fix that problem for three months contributed to the ultimate demise of AlphaNT, since we'd already shipped Intel and MIPS versions, and Pro/E was THE NT app of the day.
Yes, I'm delusional, I'll admit it, but those were good times. 32MB of RAM and 1GB hard drives.
Seems like other than some interesting history on the development of NT, we're all pretty happy to dump whatever version of Windows we were using and purge it entirely from our memories :)
That, and there's not much legendary or esoteric about Windows!
