I don’t know to be honest. But maybe the BIOS is too old?
I have a PC10 that had an old BIOS that was so old it was unable to load any Option ROM (VGA BIOS etc.).
Upgrading it solved many compatibility issues.
Maybe it helps to install an IBM PC/XT ROM or a late PC ROM, too?
- I mean, something already works. If the HDD controller BIOS wasn't loaded you could access to the HDD via DOS booted from floppy, either.
Again, I'm just a layman here.

sounds like maybe the partition isn't active? try setting it active in FDISK

If it worked before and now doesn’t the hard drive is probably getting tired, the grease hardens and until it heats up a bit you can’t boot.

I had a really tired drive, would, turn system on, boot off floppy, wait a few minutes, use a hard drive parking utility then reboot.

Then it would boot off the hd and work normally

On old drives you need to be careful not to do much with them until they warm up or you may corrupt a partition, boot files, etc

Another idea: If the HDD was formatted using MS-DOS 2 or 3, it can be that modern SYS of a modern DOS has trouble (FAT12 or FAT16 with strange values).
Re-formastting it using FAT16B might help. It's just a farfetched idea, though.

Jo22 wrote on 2025-11-26, 16:53:

Another idea: If the HDD was formatted using MS-DOS 2 or 3, it can be that modern SYS of a modern DOS has trouble (FAT12 or FAT16 with strange values).
Re-formastting it using FAT16B might help. It's just a farfetched idea, though.

This

Just sys’ing a drive from a very old XT with unknown history is a recipe for frustration

rmay635703 wrote on 2025-11-26, 16:14:

If it worked before and now doesn’t the hard drive is probably getting tired, the grease hardens and until it heats up a bit you […]
Show full quote

If it worked before and now doesn’t the hard drive is probably getting tired, the grease hardens and until it heats up a bit you can’t boot.

I had a really tired drive, would, turn system on, boot off floppy, wait a few minutes, use a hard drive parking utility then reboot.

Then it would boot off the hd and work normally

On old drives you need to be careful not to do much with them until they warm up or you may corrupt a partition, boot files, etc

Ah, this is a great suggestion! I went a very very long time without powering on my 5150 and the Miniscribe 20MB is back to giving me the silent blink-of-death. It did this when I got it and I was able to open the drive up and mess with the worm gear to get it running again. It's possible that booting from a floppy and running the park command repeatedly will get it moving, but I'm not sure how that works if the drive isn't functioning enough to boot on it's own.

If I don't have to open the thing and risk getting dust in it (again) that would be fantastic. 😌

I have no advice other than do a fresh low level format and DOS format (DOS 5 is best for this machine).

maxtherabbit wrote on 2025-11-26, 14:26:

sounds like maybe the partition isn't active? try setting it active in FDISK

This was the best idea. I started FDISK, set partition as active and now everything is working.
By the way as a graphic card I used Trident 8900 and it also is working fine.