Problems formatting USB3 drive as bootable FAT32

[Dromeno]

My toshiba external USB drive (USB3) becomes unreadable for windows pc's and macs when I format it as FAT32 and flag the partition as bootable. When I remove the flag windows and macs recognize it again (!?). Puppy has no problems with it but without the flag it can not boot, and with the flag puppy is the only os which can read it.

I have tried to make two partitions on a USB hdd before (one with the portable OS and the other for storage) but then the storage partition is not read when the machine is booted from the hdd.

I guess I am overlooking something but I have no clue what yet. Is there anybody willing to help?

[Karl Godt]

Why Fat32 ?

Partition Layout ?

Size ?

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Bootable flag is needed for extlinux or isolinux . Grubs do not need the bootflag set .

[Dromeno]

Good that I do not need the flag set for grub4dos. Didn't know that!

Fat32: the external disk needs to be usable for Android/Linux/Mac/Windows and I thought that f32 would be the best option for that purpose.

[Burn_IT]

Try setting the boot flag from Windows and see if that makes a difference.