Unable to boot from a external HDD to install windows 7

To cut a long story short, i followed the steps here : http://www.intowindows.com/how-to-install-windows-7vist... so that i can install win 7 64 bit off my external HDD.

When i select to boot from the external drive however, i just get a blinking cursor for a second or two and then windows starts up as normal.

Anyone have any ideas what to do?

The DVD/USB tool does not detect my external drives so i am using the command prompt method instead.

ISO is the official win 7 ultimate 64 bit downloaded from the microsoft site.

I was able to boot from and install windows from this external drive before but it just mysteriously stopped working.

Try one of this tutorials.

For Legacy BIOS:
USB Windows 7 Installation Key Drive - Create

for UEFI/BIOS firmware:
UEFI Bootable USB Flash Drive - Create in Windows

Unfortunately the tutorial you linked is exatly the same as the guide i linked (which means i already did all the same steps).

Not sure what the UEFI thing is...how do i check i have it? The BIOS interface looks the same as a standard BIOS one.

Edit ; Nevermind, i just checked, i'm using a BIOS called american megatrends, pretty sure its legacy BIOS.

An external HDD is detected differently than a USB flash stick so is much harder to format as a bootable installer. I would not waste my time as it is nearly impossible with no known method that works for all models. Use flash stick or DVD.

But i was able to boot using this same hard drive before. I dont know why its not working now.

I also just noticed some very odd behaviour with this installation of windows.

-All the files that i download instantly dissapear once the download finishes

-I cannot access microsoft security essentials or bit defender. The former complains that i do not have permission, the latter tells me that i may not have permission.

Im thinking i might have gotten hit with some kind of virus....

And the DVD drive is not showing up in windows explorer....

Back up any files to quarantine and don't reimport them later until they've been scanned with Malwarebytes and MSE.

Boot Win7 installer from Step 1 to write to stick or burn to DVD using tool in Step 2 of Clean Reinstall - Factory OEM Windows 7.

Delete all partitions during booted Custom Install.

Problem being i can't boot the windows installer at all. I dont have any DVDs or USB sticks to write it to.

Use some of the hundreds of dollars saved on a repair bill by coming here for help to buy a $5 flash stick or $2 pack of DVD's on the wall rack at Walgreens.