First there was windows 95
Then windows 98
Then windows 98 SE (second edition)
Then windows 2000
Then windows Me
Then windows XP
Now windows vista which is allot like windows me which makes users say Windows ME SE as windows me was a total joke.
That wasn't the way things went in the evolution of Windows:
First, there was Windows 1.x. It sucked. Windows 2.x came out, and it was also pretty bad, but not as bad.
Windows 3.0 came out, and it wasn't that horrible. It sat on top of DOS, and in general, people would either run Windows, or exit Windows to run DOS apps. Note that this was the first time there was even SOME 32 bit support, the OS(just a graphical user interface since it ran on top of DOS) started as a 16 bit, but as time went on, more 32 bit stuff was added.
Windows 3.1 as the name implies was an updated Windows 3.0, and with it came scalable fonts(so you didn't have to select the sizes when you installed, they could be scaled at any time). Windows 3.11 and Windows for Workgroups were just updates for Windows 3.11. There was an increased support for 32 bit drivers and parts of the OS were also starting to get the 32 bit treatment(while still being allowed to run on 80286 based computers)
Windows 95 was primarily an upgrade from Windows 3.1, with a new UI. It was still Windows on top of DOS, but for the first time, you didn't need DOS in addition to Windows. There was enough 32 bit code by this point to require an 80386 or better processor, so the 286 was dead at that point.
Windows 98, 98SE, and ME were all just updates from Windows 95, though ME took away the ability to boot just to the DOS prompt, even though it was still "Windows on top of DOS".
Now, along the way, Microsoft saw the design of computers, and Windows, and decided that the OS would be a LOT faster if they coded an OS based on 32 bit, without taking off from a 16 bit code base. So, Windows NT came along. NT stood for "New Technology", and while it had some advantages, it had issues with compatibility when it came to DOS and Windows 3.x applications. In time, NT went through it's versions, 1.x, 2.x, but it took until around 3.5 or so before it started to really "make it".
Eventually, Microsoft wanted to do away with supporting two different operating systems, so they planned to merge the two operating system lines. The plan was that Windows 2000 would offer compatibility for most DOS and 16/32 bit windows applications while staying a pure 32 bit OS. It just didn't happen for 2000 though.
Windows XP is what Microsoft wanted for 2000, a true merging of the business OS line and the consumer OS line. And so it happened. Windows XP really did what it was supposed to(with some very old programs not working).
Now, Vista adds a bunch of stuff, but at the same time, changes enough things that it breaks the compatibility that made Windows XP such a good upgrade. This is why Vista isn't doing well, it breaks more than it adds when it comes to being compatible. NEW programs will be fine, but people don't like needing to replace older programs, especially when those programs no longer exist(the developer and/or publisher has gone out of business).
Windows Vista isn't really all that bad, it's just bad for those who think about upgrading. If your new computer and printer have proper Vista support, and you don't run DOS or older Windows applications, Vista may seem better. It's only those who have old applications that have anything to complain about.