Maybe.
I bought a Windows 7 Pro 32 bit OEM disk from here:http://www.discountmountainsoftware.com/miwi7prfuveo5.html?cmp=nextag
The Windows 7 DVD is branded with a Dell logo and comes with a valid key and license. Activation instructions were enclosed with the disc in case online activation fails on the first try. The instructions worked perfectly.
Now when I boot up, my welcome screen has a Dell logo on it. Whenever I need to run a Windows Genuine Advantage test in order to download Windows Updates, there are no problems at all. As far as Microsoft is concerned, I have a 100% legal and genuine copy of Windows 7 Pro.
Using an unbraded disc vs an OEM disc is different though. I use unbraded discs all the time with OEM keys and it works because it's supposed to. Not the other way around.