Is it possible to make a USB pen drive come up as a "hard drive" under Windows Explorer and when looking at it in the BIOS?
No, I don't believe so. The reason is that the BIOS (and Windows) detect that it's plugged into a USB interface, not a SATA, IDE, or SCSI interface. It has nothing to do with the formatting or the file system--the file systems used on USB drives are already the same as used on hard drives.
Why do you want this behavior? Are you just annoyed by the different icon you see in Explorer, or is there a more practical reason to care?
You can probably use plop to get a cd, floppy or other media to bootstrap the USB drive. Alternately, read on
Both approaches involve formatting your drive.
Before you go around trying to disguise your pen drive as a removable drive (more on that later), h, i'd suggest giving the HP drive tool a shot - it almost ALWAYS works, and makes pendrives bootable, and is less risky than flipping the removable drive bit
If that dosen't work...
There is supposed to be a way to make it turn up as a removable hard disk - using a bit of software meant for, and by lexar called 'bootit' - it filps the removable drive bit. Unfortunately, its impossible to find - there seems to be a copy here - it used to be on pendriveapps but its gone.
As with random tools, use at your own risk - there's no support for it at this time (lexar dosen't host it any more, and it was meant for their drives), and there's no guarantee it'll work for your specific drive or needs.It should, in theory make your pendrive appear to be a external hard drive.