Formatted USB flash drive in Disk Utility, now it won't show
I am trying to help my mother bring her old but still working 17-in MacBook Pro up to date with OS X (she's on 10.5.x).
In order to install OS X 10.6 (as a precursor to later OSs), I tried to format a USB flash drive with a plan for a GUID partition as instructed online, onto which I would put a disk image of the OS installer.
However, I formatted the USB drive as Mac Extended (journaled) and could not find the GUID option in Partition, so I reformatted as Mac Extended (case sensitive) and now the drive does not show either in Finder or in Disk Utility.
The USB drive was fine before. Now it looks like Disk Utility has ruined it.
Any solutions?
MacBook Pro, Mac OS X (10.5.6)