Not sure how exactly you setup the drive.
But one issue can be what partition table type you used for the drive.
If it was gpt, grub4dos does not support that.
So in using Gparted program to setup the drive.
I would make a new partition table type msdos. (that deletes everything on the drive)
then partition and format it.
..
Note:
There is a chance that the partition table does need to be gpt type for the computer to properly see it.
But first try it with a msdos type partition table.
The boot loader that Frugalpup Installer uses will support both types. It installs Grub2 boot loader.
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This is what has worked for me installing to internal drives of any type.
You need to do all of this from a Booted Fossapup64 installed on a USB stick or a CD.
Use this to boot the computer to a Running Fossapup64.
So you can run all the needed programs in Fossapup64.
Have the Puppy version you want to install ISO file to use as source for the frugal install.
Use the program Frugalpup Installer to do the install to the internal drive.
Fossapup64 9.5 has Frugalpup already in it, but there is a newer version you may want to install and use.
Frugalpup v38 can be gotten here:
viewtopic.php?t=337
This is what I do.
Use Gparted program.
Setup the internal drive with 2 partitions.
First one, small 300MB, fat32 format, flagged boot, esp. (location for boot loader files, boot partition)
Rest of drive, whatever other partition(s), but one ext3 or 4 format. (location to put frugal installs)
(this is UEFI standard requirement, and some computers, look for a fat32 partition, for boot loader files)
Run Frugalpup Installer main program.
On the main window are selection buttons.
Select the Puppy button, to do the install.
Go through install process, selecting to install to the ext formatted partition.
Note:
When selecting the partition to install to.
A window pops up, giving option to make a directory, to put the frugal install in.
I make this directory and usually name it, the name of the Puppy version.
Carefully read that windows info.
Press enter, makes the directory, not the OK button.
complete the install.
When it gets back to the main Frugalpup window.
Select the boot button.
Select the location of the frugal install, on the internal drive. (usually this is already selected and you just have to click on OK)
Select the small 300MB 1st partition, as location to install the boot loader. (may need to scroll the selection window)
Select the boot loader type.
UEFI
mbr ->legacy bios boot
both
You can install the UEFI for UEFI computers.
mbr for legacy bios computers.
both, to boot anything.
The UEFI or both will also install the needed files, to support secure boot enabled in UEFI.
When you first boot the internal drive, on a UEFI computer, with secure boot enabled.
A process will start, to allow you to install the Puppy security key, to the computer.
It will add this Puppy key, to the other ones, loaded on the computer.
Note:
I did have one computer, that would not boot from install on the internal drive, if secure boot was disabled.
So had to make it enabled.
But no problem, installed the UEFI type boot loader, and it provided needed stuff to install needed Puppy security key.
Note:
To put more frugal installs on the same drive.
Run Frugalpup Installer.
Do the complete Frugalpup Installer process again, for the new Puppy version.
When you run the boot loader install.
It will make boot menu entries, for all installs it finds, on the drive.
If this does not work.
Need specific details of exactly what happens as it tries to boot.
It does this, then that happens, then i see this.