The HP tool...
Did you try the latest version of the HP USB Disk Storage Format Tool? The latest I found(2.2.3) was newer than the version found in your link. Might it work better? If you run it in Windows 7, try running it with Administrator Privileges.
Otherwise, if you can use the command "lshw" with root privileges in a terminal, you might be able to see who manufactured the actual HDD for Asus? If you can, there may be a HDD utility program that will low-level format the disk. ESTOOL for Samsung will do that for their HDD.
As I understand it, you havn't tried DD as yet. It's not that hard as long as you are sure exactly which HDD or partition you're working on. I don't know whether or not DD will see this hidden partition to do its job.
The Internet tells me this will the kill it, but if it does, you might have to restore the HDD msdos partition table before you can partition the disk.