Do you have a certificate of authenticity? Or did you buy your laptop from an OEM provider. OEM providers sometimes embed the license key into the computer's BIOS. You should have the restore CDs which say that on a laptop.

If you have a desktop and no certificate of authenticity, even if your license activates and seems okay, it's still considered invalid.

http://www.microsoft.com/OEM/en/licensing/antipiracy/Pages/COA_hologram.aspx#fbid=zipZ8l7kzZS

The thing that they aren't blacklisted doesn't mean they are already used or are in usage. There is no way you could get so cheap not pirated and legit licences not to mention that it usually comes with the sticker from Microsoft.

Of course, just because a key is working now, it doesn't mean it is legit. That's why I'm curious as to how we can figure this out.