You didn't really give enough information for an informed answer...but that's never stopped me...
If the disk is new or you plan to use the whole disk for W7, then you should just set it up as the second boot device in the system. Boot from the W7 Install disk and when it asks you which drive to use, pick that one. At that time you can delete existing partition (DATA WILL BE LOST!) and build new ones. format and go. Once that's done, you should have W7 running on that disk.
NTLDR error is because there is no OS on the drive yet, but there is likely a remnant of something in the MBR of that drive.
If you want to fdisk the drive and clean it up, I suggest getting a linux live cd like ubuntu or knoppix and booting from that. they have pretty easy to use partitioners like gparted that can wipe and setup your disk...just like fdisk.