Most bundles that include the ECS K7S5A and a Duron Processor can be had for under $90, up to a 1.3 GHz CPU. There is a lot of bad talk regarding this motherboard, but I just built a new system using it for my Cousin (256 MB DDR, Athlon XP 1900+) and it works just fine. If you use SDRAM, just make sure it is a matched set of name brand sticks. Try to mix it up and there will very likely be problems. Similarly, it is a good idea to make sure the case you use meets or exceeds minimum output capability, as current fluctuations run havoc with the ECS K7S5A. Minimum +3.3V & +5V TOC of 180W, recommended 220W or higher. Minimum +3.3V @ 20A, +5V @ 30A, recommended 28A & 35A, respectively.
You might save a few bucks by going with a Biostar M7VIG Pro or Biostar M7VKQ, those have integrated video, but are also mATX boards. The M7VKQ is the older of those two Biostar boards, with three PCI, one ISA ~*cringe*~, and one AMR slot - it only takes PC133, no DDR. I recently ordered a PC based on the M7VIG Pro with Duron 1300 and 256 MB PC133 for my neighbor. I loaded up the Ohio demo for No One Lives Forever 2 and though the PC ran the game, it was rather slow with glitches like missing hair using the S3 ProSavage 8 Video Integrated chipset. Luckily the M7VIG Pro comes with an AGP slot.
At around $25 you will likely only find really old refurbished motherboards that have Cyrix chips soldered on board. They will run really slow, like 550 MHz or less. Maybe, if you were donating PCs to a Central American school or convent, you could get a bunch of these together and send them ten machines for around $500 bucks... Otherwise, I wouldn't really bother with it. Some online retailers will sell you a version of the ECS K7SEM that has a so-called "Duron XP 1300" chip soldered on-board. These are really just moderately overclocked Duron 850 processors (around 890 MHz), whose name and speed is inaccurately reported in the BIOS.
HUN-YA!
Red Ronin