can't install windows on my blank new replacement hard drive

Yes, genuine dell windows dvd. It came from dell service as I ordered it.

You shouldn't need to enter a product key when used on a system that shipped with Windows 8.  (If this system did not ship with Windows 8, you can't use a Dell DVD ... you'd have to purchase Windows 8 and use "retail" media to install.)

However, if this system shipped with Windows 8 and your Dell installation DVD is giving that message, then you need to create a file called PID.txt and put it in the /sources folder of the installation media (you'll have to either burn a different DVD or install via USB).  Inside the file should be this (where the X's are the characters of the product key):

[PID]
Value=XXXXX-XXXXX-XXXXX-XXXXX-XXXXX

You can get your specific product key from the BIOS by installing Windows 7 (you can download a 30 day trial from Digital River - just google 'windows 7 iso'), then running RWEverything, and writing down the key stored in ACPI Tables, MSDM.

Or you can use a generic key to get Windows 8 installed, then use RWEverything to get the key, then activate using it.  Here are the generic keys:

http://technet.microsoft.com/en-us/library/jj612867.aspx