Microsoft was desperate for relevance in late 1999 at the height of the dot com mania. There were about a dozen technical committees that were supposed to be figuring out the future (the company leaked that Bill was personally chairing the user experience committee) which would be laid out at a press event with the grandiose name of Forum 2000. The committees were pretty much a bust in terms of delivering anything but the company still felt it had to demonstrate it had a future, so there was some furious sausage-making.

Originally scheduled for January 2000 to layout a prompt vision for the new century, it kept being delayed because of adverse rulings in the DoJ case. Forum 2000 finally happened in Redmond in June of 2000 and that was where the .NET brand debuted. Bill painted a broad overview of the coming decade that would stand up very well, even if Microsoft wasn't necessarily the company to deliver on the vision (I think it was where the Tablet PC was first unveiled). There also were specific presentations for different audiences. The developer session also stood up well and Microsoft largely delivered on it. The information worker session was pretty weak, as was the consumer session (Windows Me anyone?), though the consumer scenario video did directly lead to HailStorm as an enterprising engineer assumed it was his job to make that video a reality. Ballmer ended the event with a very reactive and competitively focused talk that was very much of the dot com moment. It took another three months or so before it was clear the bubble had popped and the world had changed dramatically (much to Microsoft's advantage).

The CLR and .NET Framework were announced at the PDC in Orlando a month later (which was notable because nothing leaked in advance so Microsoft platform developers had their entire world rocked and wandered around the event in a daze).

As for where .NET came from, the branding people presented SteveB with 3-4 options (the only one I remember was something like "Microsoft AXP") which he rejected and then bellowed out "How about dot net?" except it was both a question and a directive. Sun Microsystems was not only still around then but had lots of mindshare with its "we're the dot in dot com" campaign which Steve clearly had on the brain.

The tension with the Windows brand was palpable from the start (and it probably only got out the door because the leader of the Windows group was on sabbatical at the time). But the company rallied around .NET as employees desperately sought "a new parade" (even to a fault - the brand was immediately appropriated and misused by almost every product group, a mess that took a couple of years to clean up). And it didn't hurt that the rest of the industry was imploding along with the dot com bubble.

FWIW, Next Generation Windows Services was just Next Generation Services until the night before it was discussed publicly, whereupon Windows has hastily jammed into the name.