Windows 7 Trying to boot Windows 7 through a WD My Book on my new computer... HELP PLEASE!!

Wouldn't you have to use a Windows 7 .iso format ?

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I think this situation may be similar ?

Ok first you need a Win 7 .iso.
If you tried to copy the contents of a Win 7 install DVD to your external drive that won't work.

There is a free tool that will do that for you.

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Once you have the .iso you would then create your bootable USB device.

Microsoft recently released an updated version of win to flash.

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You might find using a 4 GB flash drive preferable to using the external drive.
If you don't have one a trip to Walmart or your local Office Supply store can get you a 4 GB (minimum) drive cheaply.
Don't go too cheap though, stick with the big brand names like SanDisk or Lexar. Less than $30.00 can get you a Sandisk Cruser Mini.
I know for a fact that (through experience) a Sandisk Cruzer will work.
Some cheap, unknown brand devices won't work.

Question are you trying to install Win 7 on your new computer, you are saying "boot" Win 7 and that has me confused?
Also are you planning on replacing XP with Win 7 if an install is your goal?

Yes, I am installing Windows 7 to a new computer. It seems that I may have to go out and pick up flash drive. I thought that it may have been possible to use the external hdd, but it seems that you cant make it bootable on a fresh computer