"If you bought the board, then you should have the instruction manual. Can you look up for me what voltage and configuration of pc2700 ram the board will accept? Specifically, I'm looking for what type of 512 MB stick it will take. I think it would be 2.5 volt 64x64, but i'm not sure. I'd really appreciate it "
Actually, pretty much any 512mb DDR stick will work. They are all 2.5v and both double sided and single sided will work. Any of the high density memory you get in a 256mb or 512mb stick will most likely be double sided.
As far as DDR333, or PC2700 as it's more commonly known, it isn't really needed on this board. First, if you get PC2700, your FSB of your Athlon will run @ 133mhz (266DDR) and the board will run the memory at 166mhz(333DDR). This may sound great and you would think that it would be much faster than running both the FSB and memory @ 133...but it really isn't. Sure, in the benches you may see a slightly better score, but in real world use it is not even noticeable. This is mostly due to two reasons. First, the Athlon can't really use the extra bandwith of PC2700 unless it is also running a 166mhz(333mhzDDR) FSB, and to do that you would need to unlock your CPU so you could lower the multiplier and raise the FSB. Secondly, when you run your memory bus asyncronusly from the FSB, you introduce a good deal of latency. This latency offsets most of the boost from the memory running faster. Think of it this way...even if your memory is running @ 333mhz DDR, the FSB is still running @ 266mhz...so when data travels to and from the memory via the FSB, it hits a bottleneck of sorts since the two busses are not running the same speed. I hope I explained that well enough.
Anyway, my point is this. If you have the extra cash for PC2700, go for it...but it's really not needed. You won't really notice any speed difference except in a few benches, so it's up to you. However, if you plan on unlocking your CPU, go for the PC2700 and run a 166mhz FSB and 166mhz memory bus.
Also, to answer a few of your earlier questions, yes you can use your 1.4ghz 266mhz FSB Tbird just fine on the board until you get an XP. Once you get your XP, you can simply swap CPU's and you will be good to go. No need to reinstall windows or anything, a CPU swap doesn't require any changes.
Now..as far as your questions on DDR speeds.
PC1600=100mhz=1.6 GB/s bandwith
PC2100=133mhz=2.1 GB/s bandwith
PC2400=150mhz=2.4 GB/s bandwith
PC2700=166mhz=2.7 GB/s bandwith
Now, for a 1.4ghz Tbird, DDR will work fine. You want at least PC2100 since your FSB runs 133mhz. The PC1600 is for use with 100mhz (200mhzDDR) FSB athlons.
As for the type of memory you want, you want unbuffered, non registered, non-ECC DDR. Stick with some name brands like Crucial, Samsung, Kingmax, etc and you will be fine. If you have a certain module in mind, just post the link and I'll check it out for you.
That's should get you going. If you need any more help I'll keep an eye on this thread...