If you are looking for DVD drivers, you don't need them. Simply plug in the drive, it will work.
If you are looking for a DVD of Win7 ultimate then it can be purchased at your local computer store, or online.
If you are looking for an illegal copy of win7 then please look elsewhere. If you want windows, then you have to pay for it. Win7 is worth nearly every penny you spend on it, and if you cannot afford it then there are tons of great/cheap/free versions of linux to try.