So I did a little research on that USB device and couldn't find out for sure if it contains a hidden partition or not. But... the next suggestion is a rather long process to fix this problem, but if you want to boot from USB, here's what you need to do.
So, from what I can tell, Gparted is the only program to date that will allow you to view and modify hidden partitions on flash devices. The only problem is that GParted is only on linux. Before I walk you through downloading VMWare, Ubuntu, creating a Virtual Machine, installing GParted in that Linux virtual machine and then modifying the USB drive... let's try one more option beforehand.
Download the GParted package here
. You'll want to select the .zip file to download. Once complete, extract the files. In the directory that it's been extracted to, navigate to the \utils\win32 folder and select the makeboot.bat file. Copy this file to your USB stick before you run it!
A .bat or batch file will execute in the directory it's run from, so you don't want to run this from your Windows download folder as you'd be running the batch file on your root drive. When you run the batch file, you'll get a Command Prompt (console program) that executes the commands. Confirm that the drive letter listed is the drive letter of the USB device. Once that completes, copy the files from the Windows disc to the USB device and try once more.
---------- Post added at 11:07 PM ---------- Previous post was at 10:31 PM ----------
I'm not sure how effective it is, but I've also read that the HP USB Format Tool
(windows based) will remove the hidden partition from a USB device. You can also try this before you use the makeboot.bat file.