It came already activated with my new PC. I formatted and installed Vista.
So, in my eyes it's legit. To make it fully legit I will send by post a screw from the PC Fan to quicksilva to comply with the OEM policy.
Unfortunately, that still makes it not legal in all likelyhood -- aside from the catch that an OEM version of the OS has to come bundled with hardware, there's also the snag that it's not transferrable to another system at a later date, not unless you bought the entire hardware package it was originally bundled with.
Newegg shows the following for any of the OEM versions:
"Disclaimer: Qualifying proof of purchase must be recent receipts showing the purchase of a mother board, hard drive, RAM and a CPU. The components can be on multiple receipts; not necessarily all on one receipt nor on the same receipt as the qualifying Windows XP/Office 2003 that you purchased."
There used to be a ton of places that would sell OEM windows with a bunched $0.05 CD-rom audio cable or the likes, but it looks like they're cracking down on that now.