I find it ironic that this question was asked just under a month ago, as I just came across a similar situation, unexpectedly. I had been running an Athlon 1.33GHz, when a new video card prompted me to upgrade to a new, but cheap motherboard. There aren't a whole lot of Socket 7/462 motherboards left on the market, but I found one that met my needs.
Much to my surprise, when I got home and opened it, there was already a CPU/heatsink/fan mounted in it, totally undocumented on the box or in the manual. It wasn't a return for which someone forgot to remove the cpu, as the heatsink clamps had been spot glued with silicone, and the lever had been taped down with a "do not remove this label" strip, which also hid the AMD label on the chip. When I fired it up, the motherboard reported it as a 1.8GHz Duron.
Given the responses here, and some related reviews, I'm going to stick with it for now. I can't speak for the original poster, but in my case it's a bit of a pain to swap CPUs for testing purposes. I don't trust the motherboard supports for the pressure needed to release the heatsink clamps, so it means taking the motherboard entirely out, swapping CPUs, and putting it back in. Eventually, I'll just get more memory so I can fire up the old board in a separate case, and then do a comparison.
Gary