Mike's PCjr Page

No problem. Just make sure that you create a Primary partition; Windows 7 can't read Extended partitions (and DOS can't boot from a logical drive in an extended partition anyway so it shouldn't come up in practice).

Trixter wrote:No, it needs to be formatted with a patched DOS 5 or higher so that you can boot off of it on the PCjr. DOS versions 5 and later don't boot the PCjr unless you patch them.

DOS 3.31 is actually Compaq DOS 3.31 and I believe it needs to be patched too.

You want to stay away from 3.3 and lower because they only support partitions 32MB in size. 3.31 and later support 2G per partition.

I'm pretty sure I've used Compaq DOS 3.31 on my PCjr without patching it...

3.1 to 3.3 don't need patching, but 3.31 is a special beast that adds FAT16 support. I don't recall if it needs patching -- if it doesn't boot, patch it :-)

In case anybody at home is keeping score, I was able to acquire a copy of DOS 3.3 off of ebay for a very reasonable price, was able to format the CF card in FAT, thereby enabling Windows 10 to see it, moved over img2dsk and the patched DOS 5 disk image, create a bootable floppy from it, and start all over again, this time using DOS 5 and being able to use the max size of 2 gig! Woohoo!

I got a used 1GB DOM on eBay, made by Silicon Systems apparently. The jr-IDE can't detect the DOM all the time so I assume I'll need to find something else, but when it does detect it, it shows 4 non-DOS partitions (according to DOS 2.10 and 3.10) and I can't format the drive or delete any partitions.
Also as an experiment I attempted to boot off the DOM and see if anything would happen and I got a crazy screen full of garbage. Does this mean anything to anyone? https://youtu.be/mYfSzr9KT4E

Regarding the partitions and booting garbage, I think that's just a symptom of the existing data already on the DOM (you bought it used). You should boot DOS, run "fdisk /mbr" (if your DOS supports that, then run fdisk and just erase every single partition, then create a new primary one, then let fdisk reboot the system, then "format c: /s", then reboot. That should work.

I'll have to get a patched DOS to use then, because both versions I have on floppy don't allow me to do anything to those partitions. Guess I'll try that tomorrow.

I had the same problem with a Hyperdisk DOM on my jrIDE with PC DOS 3.3 ... I used the attached DEBUG script to clear the non-DOS partitions and then ran FDISK/FORMAT. Worked perfect. Hope this helps!

Thanks! Once I got the power issues sorted out with my DOM, the debug script worked great!