Returning bootable flash drive to normal?

I have found this topic already: http://www.sevenforums.com/general-discussion/18317-help-bootable-usb-disc-back-normal-usb.html
but it did not solve my problem.

I followed the directions on this tutorial: Install Windows 7 From USB Drive/Pen Drive
to make my 8GB flash drive bootable to put W7 on my sister's computer which has a DVD drive that won't read my W7 DVDs for some reason.

Now I need to return my USB flash drive to normal, except that it only shows up as a disk drive. I can't right click and format it as the computer wants me to insert a disk to format. I am also unable to format the flash drive using Disk Management, where it is also showing up as a disk drive, but with no media inserted. What am I missing? I hope I have not forever ruined this flash drive.

A little bit more information...
When I plug the flash drive in, it is showing up as a "Device with Removable Storage" like a CD/DVD drive. If I try and make any changes to it or open it my computer tells me that there is no media in the drive.

I've also tried to access it from the boot menu in BIOS and was told that it isn't a bootable device. I'm really at a loss here.