Windows 7: Installing Windows 7 off of an external HDD..

How would one go about doing this? I'd like a fresh copy of Windows 7 on an internal hard drive (with Windows 7 already on it) and I have a 500GB external hard drive.

This should allow you to do what you want.

Install Windows 7 Without Using Any External Device

You can mark the external Active in Disk Management, extract the ISO files to it using ImgBurn or PowerISO, then boot it using BIOS boot order or one-time BIOS Boot Menu key.

This allows you to use the Custom>Drive Tools to repartition and format before install, since you are booting the installer as required.

Some USB drives require bootsecting, which can be achieved by writing the ISO to it using UltraISO trial version's Bootable tab.

You can also from Windows 7 run Setup as Admin from the external drive but you won't have the Drive Tools available as when booted.

Petey7, your guide mentions extracting the Windows 7 iso to "a partition or drive on which you are not going to Install Windows 7"

What drive would that be

That would be the external hard drive you spoke of in your original post.

EDIT: I know the title is misleading, but it should work for using an external hard drive.