Can't help you with the AT form factor. But if you plan on going with the Intel 933MHz I'd suggest looking into EPoX's SPA3L motherboard. It is an 815EP chipset. I've been thrilled with mine. Though I don't tend to overclock, it would be very easy to with this board.

if you want a p3 933, you must change your case, because there is no baby at that support p3s.

I have p3-933 system right now and I am using Abit SA6R (Intel 815E chipset). This board is great for overclockers because you can do it through Bios and it has SoftMenu III for sigle MHZ increment. The only problem with this board is that you can have only 512 mb of total RAM. I already reached that limited now. =)

It isn't just the Abit board. The 815 chipset only handles 512meg RAM. I just maxed mine out today. But considering my PIII 450 only had 128meg (until I pumped it up to 256 today), I'm not going to complain. Running at a heavy load, my system still has 400meg to spare.

Well, I hate to break it to you, but if youre gonna upgrade, you'll have to buy a new case-mainly because boards are being made in ATX or micro-ATX formfactor. All the high performance boards I know of come in the ATX size. AT along w baby AT have been abandon it appears. If you want to put in tons of memory with an Intel, you'll have to go with a VIA Apollo Pro 133A. I suggest the Tyan Trinity cause its got slot 1 & socket 370 and can support up to 1Ghz P3s. Its not meant for overclocking, but I have had no problems with it whatsoever. On the AMD side, skip DDR because: 1. Its expensive 2. Right now most everything cant use the bandwith so your just throwing money away; and 3. The VIA KT133A chipset supposedly provides nearly all the perfomance or all of it WITHOUT DDR, so they say. The FIC AZ11e is nothing special, but it does the job. If you're willing to spend a little more, go with the Asus A7V133 or the Abit KT7A board, both have an extra ATA100 controller, but the Abit provides Raid 0,1,&0+1 on the controller.
Since you'll have to get a new case, get something with a 300 Watt PS. 250 Watt is good but with the juice the T-Bird requires, its best to be on the safe side. Also get a good cooler, if you havent heard, the current Athlon and Duron chips have some heat issues and will fry in seconds with no heatsink/fan combo, while Intel's chips have some sensor right on the die to tell you.
You can go with Intel's shoddy 820 chipset or the 840, but both require extremely expensive RDRAM. I would say go with a board with a VIA chipset if you go with an Intel processor just because you can load them up with at least 768 megs of ram. If you go AMD, VIA is the only choice, because SiS chipsets suck compared with the VIA KT133/133A chipset, well SiS sucks in general.
As far as nVidia and Win2k are concered, I'm no help, I use a card from the company formerly know as 3dfx called the Voodoo 4 4500 AGP. Dont laugh, cause I havent heard of problems concerning them. I do believe nVidia drivers for Win2k work just fine, though
When you upgrade you're gonna have to get a new case,because unless Im wrong there arent any AT boards that support P3s or Athlons. Im pretty sure AT is dead. If you do find one, you can bet its not from a major manufacturer like Intel, Asus, Abit, or any others that are mentioned on this forum.
Good luck.
 
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Whaazzzupppppppppp!
Asus A7V
Duron 600@680
384 MB SDRAM PC133@113MHz
Samsung 48x CD-ROM
Toshiba 12x DVD-ROM
Zip CD650 USB 4/4/6
Zip 100 USB
Maxtor 20.4 GB ATA100
Voodoo 4 4500 AGP
Guillemot Maxi Sound Fortissimo
SIIG 3 port 1394 PCI Adapter
D-Link DFE-530 10/100 NIC
Creative Cambridge Soundworks FPS1000
MS Intellimouse Optical
Kleer 17-inch @ 85Hz 1152x864x32 desktop

It is not overclockable, but it is stable, and meets ALL standards, cause it is made by the one who designs the standards - the Intle D815EEA motherboard! Totally stable! Just no frills, except it has a built-in Intel Pro 100 NIC, and Video/Sound onboard which I disable anyway.
 
but again, it is VERY stable, and meets/exceeds all standards. The only problems I have had is with software and drivers for SB Live and NV GTS.

I was afraid I'd have to get a new case; All the mobos I've seen listed were ATX, but I thought someone may know of an AT somewhere anyway... Thanks for all the recommendations. Currently, my video card is a Voodoo 3, but I know that will need an upgrade very soon, which is why I mentioned NVidia, but of course my next card, while not being a 3DFX for obvious reasons, doesn't HAVE to be an Nvidia. Anyone else with suggestions, please post them. I'll continue reading them. Again, thanks.

There is nothing 'shoddy' aboput the 820 chipset.
It had issues when it was being used together with DIMM's.
It has never had any problems when using RIMM's.
OK RIMM's are more expensive, but as with memory in general at the moment prices are at an all time low.
RIMM's are now about the same price as DIMM's were 4 months ago, seen them for sale at £1 per MB.

Also, how much faster is PC133 memory than PC100? I have a 128MB module I want to retain use of. I don't suppose PC100 and PC133 memory work together (probably a stupid question)?

Not a stupid question, and yes there is a strong possibility they will work together. I have run 2 PC133 sticks with a PC100 stick (128MB ea) at 133 and not had any problems. Just bear in mind that it's like anything else you overclock; mileage may vary.
 

 
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Regards,
 
clutch

Hmm... I never thought about having them work together by overclocking the PC100 module. My memory is from PNY, one of the higher quality companies, so it's definitely worth considering. As for the mobo, I am REALLY leaning toward the Abit KT7A with a 1GHz Athlon. Has anyone had problems with this board and a Voodoo3 or SB Live? I just want to make sure everything goes all right with my upgrade.

On second thought, maybe I'd better rethink that Abit board. I just read the topic:
HighPoint kt7a woes with win2k (help)