Just a note:
No matter what mainboard you buy, you will not likely be able to upgrade to the next processor generation with that board. You difinately cannot put a PIV in a PIII board, they use different sockets. More and more, the mainboard and CPU are a package, and you have to upgrade them at the same time.
The best bang for your buck right now, IMHO, is an Athlon Thunderbird. Check this latest price guide:
http://www.thetechzone.com/prices.asp?p=1 Now, these are the cheapest prices off the web, so expect to pay a bit more than the listed prices for most things from a good local shop.
You want to look at the Athlon's marked "PGA" in the list. Pretty cheap!
If you are tight for cash now, but plan to upgrade in the near future (under 6 months), you can get a Duron 750 for $50, then upgrade to a Thunderbird 1G or something in a few months and use the same motherboard. Still, for under $200 clams you can get a killer 1Ghz Thunderbird. Woo! Snap that puppy onto an Asus A7V mainboard, and you are off to the races.
Be sure not to scrimp on the RAM. I reccomend you buy Micron directly from their direct-sales division at
http://www.crucial.com. RAM is incredibly cheap at the moment, so buy the good stuff. A 256 MB stick of 168 Pin SDRAM rated PC133 at CAS2 is what you want. That's around $100 right now, cheaper than it has ever been.
http://www.crucial.com./store/ListModule.asp?module=168-pin+DIMM&x=21&y=14#SDRAM,%20PC133 Also, get a 300 Watt good quality power supply and a mid-tower ATX case.
If you want to save money, do it on the optical drives. Don't buy a DVD drive, it's a waste for most folks. Get a cheap CD-ROM drive for now. Worry about CD burners, DVD, and all that crap later, it's not required for a general use and gaming PC.
Video and sound are easy.
Video, get the GeForce 2 MX for the best value (read cheapest), or go for a GeForce 2 Pro or Radeon for mo power (read expensive). Sound, the SoundBlaster Live Value is the only choice. Cheap, good 'nuff said.
For the dirt cheapest and yet pretty good system do the Duron 750, Asus A7v, 128 Megs of Cas2 PC133 Ram, GeForce2 MX, SBLive Value. For a decent value, but higher priced and higher performing system, go with an Athlon 1Ghrz, same mobo, 256 Megs of the same RAM, ATI Radeon, same sound card.
Depends what fits in your budget really, but those are my suggestions.

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Sean "Lephturn" Conrad - Aces High Chief Trainer
A proud member of the mighty Flying Pigs
http://www.flyingpigs.com Check out
Lephturn's Aerodrome for AH articles and training info!
[This message has been edited by Lephturn (edited 03-06-2001).]