It's almost guaranteed that it's a cheap counterfeit knockoff. I bought a Xbox 360 AV cable from a not-so-reputable distributor once, and it arrived in a package claiming it was "Genuine MiorcSoft". Nothing like getting a Genuine MiorcSoft accessory for my YBox 520.
The only official way to (currently) get a legitimate Xbox 360 Wireless Receiver is to get it in a bundle with a wireless controller. Microsoft uses a proprietary wireless format, and for some reason they're not that interested in producing a standalone receiver for PCs anymore.
If you want a Xbox 360 controller for your PC, I'd suggest going with a wired one. You can pick one up used from GameStop or eBay on the cheap, although again - watch out for fakes! The wired controller will probably run you about $20, whereas the wireless receiver is probably around the same price, and you aren't getting a controller for that amount.
The wired controller "Just Works" with recent editions of Windows, and in some cases is the only controller that is officially supported by a game. The wired controllers work on both the Xbox 360 and the PC; there's not a separate version or any lockouts/drivers/funny stuff to worry about.
For your current situation, I found this blog post from a guy who was in a similar situation and got his drivers working. There's no quality control or any guarantee that the one you got is similar to his, so who knows if this will actually work. I also turned up one more, but it doesn't look as detailed as the first.
Remember also that if they were advertising it on eBay as the genuine article, and you got a knockoff, you can probably contact PayPal/eBay to work on getting your money back. (eBay, for instance, has a no-counterfeit policy.)