I built my very first PC with a $89 K7S5A/950 MHz Duron combo that I picked up from Fry's back in December. The system runs great and it was a great bargain but I do have some cautions.
Before buying this board, I spent months reading various forums including the Sharky Extreme forums, the amdmb.com ECS forum, the Tom's Hardware forum and the OCWorkbench ECS forum.
Based on the posts that I've seen the K7S5A can exhibit some problems such as "data corruption", lost CMOS, unrecognized RAM and odd startup problems. The actual frequency of these problems is hard to get a handle on since many of those posting on these forums are there in the first place because they ran into a problem. This good point was mentioned in a post above.
But the problems can not *all* be attributed to "newbie" builders or those with inadequate power supplies. I've seen very experienced builders systematically replace component after component, including top notch 400 Watt power supplies that have narrowed their problems down to the K7S5A.
Whether such extreme problems occur in 1 out of 100 boards or 1 out of 10,000 boards is hard to say. Certainly the K7S5A is a big seller and that alone is a factor in all of the problem reports.
But, whatever the odds, a K7S5A, like any complicated piece of electronics, is subject to odd behavior.
For that reason, I recommend that people buy their K7S5A from a local retailer with a decent return policy. I would recommend this even if you have to pay a few dollars more. I bought my board from a local Fry's for this very reason.
If mail order is still your best option I would recommend a seller like newegg. Outpost would also be a good option if their return policies are OK. (Weren't they once telling folks to deal directly with ECS for K7S5A returns?)
Also, the K7S5A can produce a crackling sound problem when paired with a PCI based graphics card. I found this out after I had bought a PCI Voodoo3 2000 for my setup. Some have cured this with a BIOS change and others by swapping PCI slots but some have found no solution. So buy an AGP graphics card to avoid this potential problem.
Finally, here's an excellent new K7S5A website to add to the others mentioned above:
K7S5A Problem Fix Guide
And here are the related forums:
K7S5A Problem Fix Guide Forums
Check out the "Problems with the K7S5A" sub forum for discussions of common problems.
Finally, I don't mean to knock the K7S5A. For myself and many others this board works great and is an incredible bargain. It's just that people should be aware that problems are possible.
Bob