It's most likely at least a PCIe 2.0 compatible motherboard. PCIe slots are almost always designated with a version number (e.g. 1.0, 1.1, 2.0, 3.0) - you probably just got the short end of the stick on whatever site you found the description for the board.
Post whatever computer you bought and I'm sure someone can figure it out.
Better yet, download GPU-Z and it should tell you the version of the PCIe slot you have.
Thanks this is exactly what I was looking for, I downloaded GPU-Z and it turns out I had a 2.0 slot. This could have been so much more simple if Newegg wasn't such a slacker