Windows 7: Old File Deletion 2nd Hard Drive

I am trying to clean up my second internal hard drive in my desktop in which I just upgraded the OS to Windows 7. My second hard drive (D) was the one that I think I had XP on before I upgraded to Windows 7. I installed Windows 7 on the 1st hard drive (C). So at this point I just want (D) to be as clean, empty as possible. But in trying to delete many of the files, it gets to the point where it says Admin approval required. I cant get past that part. I need help with this please. I dont care if I erase the whole hard drive, just want it cleaned up.

Have you tried going to start, computer, right clicking the D drive
and selecting format?

Nope. Sure haven't. What do I do from there and what will it do?

I got it. Thanks for the help!!

It will do what you are asking for. All data on the drive, for all
intents and prepossess, will be lost to you. Click full format if
it gives you the option.