Windows 10 defaults to UDF format which isn't compatible with dos and unfortunately the inbuilt burning program doesn't give you the option to change the format.
You'll need to install a burning program that supports ISO9660 Just about all of them do, including free ones like ImgBurn

The Win98 iso worked as it would have been created using ISO9660 format and burning this would have kept the same format.

Thank you for the advice! I've been trying to get it to work for an hour now and I can't figure out what I'm doing wrong.

I installed imgburn, chose ISO9660 as my format and burned the disc. No luck, still the same error. Then I tried making the files (which are just the installation files for GUS) into an ISO with AnyToISO, configured the ISO to be in ISO9660 format (not Joliet or UDF) and chose the file structure as DOS 8.3. Then I burned that ISO on to a disk and... No luck.

I feel like I'm missing something obvious here.

Older drives are often unable to read CD-RW .

Did you use CD-RW for the Windows 98 installation disk that worked ?
Did you use the same brand, speed rating and batch of disk as the Windows 98 installation disk ?

EDIT : What brand/model is the optical drive in your retro machine .
You did say you use the "same kind of disk" as for the Windows 98 installation, I just want to be 100% clear on what was used .

darry wrote on 2020-06-01, 17:49:

Older drives are often unable to read CD-RW .

Did you use CD-RW for the Windows 98 installation disk that worked ?
Did you use the same brand and batch of disk as the Windows 98 installation disk ?

Yep, same brand (Verbatim), same kind (CD-RW) and from the same box of 10. The drive itself is a very generic 48x.

SheikYerbouti wrote on 2020-06-01, 17:53:

darry wrote on 2020-06-01, 17:49:

Older drives are often unable to read CD-RW .

Did you use CD-RW for the Windows 98 installation disk that worked ?
Did you use the same brand and batch of disk as the Windows 98 installation disk ?

Yep, same brand (Verbatim), same kind (CD-RW) and from the same box of 10. The drive itself is a very generic 48x.

This is a longshot, but have you tried wiping and re-writing the actual Windows 98 installation disk that worked ? Maybe some of the disks in the box are marginal . Also, I imagine you are writing all theses disks at the same speed ?

Apparrently getting angry was the solution. I got so annoyed at the Abort, Retry, Fail choices that I kept hammering at the Retry and suddenly there it was, the directory listing. So it seems my drive is capable of reading CD-RW, but is just reeeeeally picky about when it chooses to do the reading.

Thank you for your help darry and chinny22!

SheikYerbouti wrote on 2020-06-01, 18:48:

Apparrently getting angry was the solution. I got so annoyed at the Abort, Retry, Fail choices that I kept hammering at the Retry and suddenly there it was, the directory listing. So it seems my drive is capable of reading CD-RW, but is just reeeeeally picky about when it chooses to do the reading.

Thank you for your help darry and chinny22!

My guess is that drive is dying; CD-RW disks have lower reflectivity than CD-R or pressed media and having issues reading them in a drive that's supposed to be able to read them does not bode well .

darry wrote on 2020-06-01, 18:55:

SheikYerbouti wrote on 2020-06-01, 18:48:

Apparrently getting angry was the solution. I got so annoyed at the Abort, Retry, Fail choices that I kept hammering at the Retry and suddenly there it was, the directory listing. So it seems my drive is capable of reading CD-RW, but is just reeeeeally picky about when it chooses to do the reading.

Thank you for your help darry and chinny22!

My guess is that drive is dying; CD-RW disks have lower reflectivity than CD-R or pressed media and having issues reading them in a drive that's supposed to be able to read them does not bode well .

Good to know, I'll start looking for a good deal for a new period correct drive.

EDIT: Though first I'll try cleaning the old one. Maybe the read head is just a bit on the dirty side.

I don't know why but failing CD drives always got me more angry then floppies back in the day.
Unless your going for period correct build I'd actually avoid a period drive, as darry said the earlier drives have trouble with burnt discs, plus general wear and tear on older drives.
DVD drives or even burner's will have better success rate with RW discs.

Large hard drive's and networking is the answer these days though! Optical drive is still good to have but copying iso's over a network is much nicer to work with 😀

chinny22 wrote on 2020-06-02, 09:34:

I don't know why but failing CD drives always got me more angry then floppies back in the day. Unless your going for period cor […]
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I don't know why but failing CD drives always got me more angry then floppies back in the day.
Unless your going for period correct build I'd actually avoid a period drive, as darry said the earlier drives have trouble with burnt discs, plus general wear and tear on older drives.
DVD drives or even burner's will have better success rate with RW discs.

Large hard drive's and networking is the answer these days though! Optical drive is still good to have but copying iso's over a network is much nicer to work with 😀

Is DOS a limiting factor here, or does it work with DVD -drives also? I don't know why, but I've had this idea in my head that DOS and DVD drives don't like each other.

I'm actually getting ready to set up a network. I've order a 3C509B-C networking card and trying to find a decent tutorial on how to setup DOS - Windows 10 network. If you know of one, I'd love a link.

Nah dos is to dumb to even care 😀
You wont be able to read DVD's but as drives are backwards compatible as far as dos is concerned it's just a CD-ROM

Dos to Win10 (well dos to anything) is tricky to network easiest way is to use ftp
https://www.youtube.com/watch?v=CgATAo9WVHs

Win98 to Win10 can be done, still a bit of a battle though.

I use a DVD-ROM drive in my 486 test bench. Works fine. In every later build, I use a DVD-RW but don't use rewritable blanks. I make Norton Ghost images of fresh installs and specialty installs, so I need to be period incorrect. Lately, some of these drives have been failing, so when I see a NOS IDE beige DVD-RW drive for a good price ($20 shipped), I usually jump on it.

chinny22 wrote on 2020-06-02, 15:56:

Nah dos is to dumb to even care 😀

Well that opens up a lot of possibilities!

Dos to Win10 (well dos to anything) is tricky to network easiest way is to use ftp
https://www.youtube.com/watch?v=CgATAo9WVHs

Thank you! This actually seems like a fun project. Sure seems a lot easier than fiddling around with CD:s and floppies.

boxpressed wrote on 2020-06-02, 16:29:

I use a DVD-ROM drive in my 486 test bench. Works fine. In every later build, I use a DVD-RW but don't use rewritable blanks. I make Norton Ghost images of fresh installs and specialty installs, so I need to be period incorrect. Lately, some of these drives have been failing, so when I see a NOS IDE beige DVD-RW drive for a good price ($20 shipped), I usually jump on it.

That's good advice. I set up a few searches on a local selling sites for beige DVD-drives.