OEM (or "white box") copies of Windows are exactly the same, without all the extraneous retail packaging. They're intended for installation on a PC without Windows pre-included, such as when you build it yourself.
Many times, the resellers will also include some minor piece of hardware (like a $5 floppy drive or some such piece of otherwise disposable crap) to keep within the strictest limitations of using OEM software.
As long as it's previously unactivated, it installs and runs perfectly fine. You can ignore any disk labeling (like Dell or HP). It's meaningless as far as the ability to correctly install & use.