I am not technical and am trying to reformat the internal memory of my GPS and reload firmware. I downloaded RMPrepUSB and can see the drive I need to format.
Got the right set-up (from a site in French) :
Post a link to that site please, this one?
Those settings are to make a "bootable" DOS "superfloppy" but without copying system files.
At first sight I see no reason why you would "need" RPMPREPUSB to obtain that (and I doubt that an original GARMIN has a DOS bootsector code).
Additionally the Author (and also some of the comments) seem like not really knowing where their towel is.
I have no idea how the device is setup from factory, but it is EITHER:
the RMPREPUSB settings described would make a non-partitioned device, so the references in the comments about a wiped partition table or about re-partitioning are not accurate.
There are several other tools that can be used to format that thingy, but using the RMPREPUSB ha been reported as working, the actual settings are here:
1. Partition size to MAX
2. Volume label to GARMIN
3. Tick Set partion as non-bootable
5. Bootloader options to MS-DOS Bootable (IO.SYS) (CC3 and CC4DOSUFD)
6. FAT32 and Boot as FDD (A: no MBR) only
7. Untick Use 64hd/32sec if possible
8. Untick copy OS files and untick BartPE -> drive
9. Click prepare drive.
not very different from the one you posted, still the result will be a "normal" FAT32 superfloppy, only non-bootable.
But the failed access "device not ready" is independent from the settings.
Which OS are you running?
Which specific model is "your GPS"?
Where (if available) is the "firmware" available?