WinXP (for slowpokes) -> Win2K (for all) -> WinNT (for max speed)
Linux (for geeks) -> BeOS (for dreamers “as it should be”)

Games are not the best usage for SMP systems 😉

You could give NT4 a go. I had friends that gamed on it back in the day. From recent experience with NT4 though it's definitely a challenging operating system to setup and use. Win2k is probably a safer bet, and I gamed a lot on that platform, probably my favourite OS.

I guess you have multiple systems, so dual boot W98/2K is not necessarily important?

A vote for 2k then, most compatible/versatile and still snappy.
But XP SP1 with all bells and whistles turned off could be just as fast.

I had XP installed on a P133 / 64MB / Banshee PCI for my dad in his garage for John Deere EPC (parts program), it ran.

I used to run a 98lite/NT4 dual boot, single CPU, and under NT4 OpenGL was faster than 9x on my TNT. I replaced the dual boot with Win2k once I got a copy (thanks, The Tower FTP, I miss you. She was my first love, er, first dodgy FTP server account).

I also have, in storage, probably now dead, dual P200 on a Tyan board. That started as dual P100s, and with searching slowly got it to the fastest the board could take. That machine ran NT4, a software firewall, with a PCI ISDN card as my home internet gateway over 20 years ago. The amount I spent to get something better than dial up! 64k each way, or 128k at twice the phone call costs, was stunning for the time.

I was Low Ping Bastard, I'm ashamed to admit 😀

I did try 2000 on the dual pentium, and what I remember was the install being staggeringly slow. I guess that is single threaded? The text boot during install I think doesn't use the SMP HAL. 2K didn't last on the machine, it ended up running NT4 Terminal Services Edition and being the file server for MP3s. Ripping station too, had SCSI Plextor drives in at some point. I did find a copy of LAME compiled for SMP, too.

With either NT4 or 2k, that dual machine was very snappy for a Pentium based system. 128meg of RAM helped.

Games back then did not use SMP, and Quake 3 was a famous example of one that did. No chance getting any performance out of that on a pentium, though. And I think Q3's SMP implementation wasn't great.

Probably best for gaming is to use the machine as a server. Running many dedicated servers on it at once would be the best use of resources. Some 9x-only games with a dedicated server mode might work on NT, too. Don't put them on the internet, but I hope you already knew that 😀

Sounding like win 2k will be the one I will use, which service pack? Or rtm?

SP4, and I think the a final pack of updates if it exists.

Unless someone know of a major show-stopper, I can't think of why you might not want to be as up to date as possible. Win2k wasn't quite as DRM'd up and anti-user as later versions of Windows, and there was never a major overhaul like before and after XPSP2.

IMHO the best version of 2k on the desktop was 2k Server 😀 Once you disable server features/services, set foreground programs to be prioritised, it is great. Same as Pro, but with Terminal Services as a choice. And not a remote desktop like XP, actual multiple GUI sessions at once.

I guess people have a wide range of tolerance but I found Win2K to be very sluggish on a dual Pentium Pro running 233 MHz. Those were even the 1MB cache versions.

And I was building Pentium II Xeons for NT4 once upon a time so I don't really think of that as something for Pentium MMX either.

NT3.5 seems more appropriate. More likely to actually be fast.

With 512Mb RAM Windows 2000 would be the best choice.
If you want to run some games.

Windows NT 4 is faster but the lack of directx support is a real problem.
Unless you only play OpenGL or glide titles.

I have Win98 and NT 3.51 on my dual PPro 200.
Win98 for gaming including dos games
NT 3.51 for messing around with server software. NT4 would be fine as well but have another PC for that.

On my dual P3 I run Win2k and 95% of my win9x games run just fine, I actually prefer it over Win98 now as 2k behaves so much better then 98.
Just not sure how much of a performance hit you'll get as 2k is a bit more resource heavy then 98