That 2900+ is a genuine Barton XP. It is based on the 2800+, but modified to operate at 400MHz, thus the 2900+ designation. It is an OEM "contract" product and was never intended by AMD to be sold as a separate part in the retail market. By example, an OEM manufacturer (such as HP or Compaq) can contract for large production runs of non-standard CPU's, making them "brand exclusive" and sometimes "model exclusive" - meaning that they are intended to be deployed in a certain make, certain model of computer. However, if the OEM's projected sales targets were off, they still take delivery of the parts, even if the computer for which they were intended is discontinued. These excess parts are sold off (dumped) by the OEM.
The upside is that they can be purchased at relatively attractive prices - or bundled, as in this case, to make them appear so. But here's the downside... AMD will NOT provide any warranty or support for these CPUs to end users because their agreement is solely with the OEM who contracted for their manufacture. These CPUs will not even appear in the tech support database if and when you call AMD for help. (I was fortunate to have gotten through to a fellow who happened to know.)
Okay, that's what AMD told me. Taking it a step further, now it makes perfect sense why a user would have a problem getting the mobo bios to properly ID the chip. The CPU's were always intended to be propietary to the specific OEM who contracted for them. So unless you know which OEM was the original purchaser, and have the specific motherboard from that OEM with the "custom bios" to ID the chip, you'll likely find it difficult to ever get the CPU to be properly recognized.
This does not necessarily represent a "bad deal," but as they say, "You pays your money, you takes your choice."