The Dell branding does not mean that it will not work. The Dell DVDs activate only on OEM keys, so if you have a PC with an OEM key on a label (which is typically for the big manufacturers) a clean install should work and once you enter your OEM key it should activate.
If you don't have an OEM key label or a legitimate key to work with you are pirating Windows no matter what disk you use.
There are really 5 types of activation for Windows Vista/7: OEM, Retail, Upgrade, Enterprise KMS, Enterprise MAK. You should be aware that OEM keys only activate on one cpu type either 32 bit or 64 bit but not both, whereas retail would activate on both.