check you've configured the other drives in the BIOS.

Which drives can you see, and what are you expecting to see?

If the drive exists and is configured properly, you'll be able to access it. Nothing to do with autoexec and config unless they are specialized RAM drives or something which I doubt.

Are the drive partitions larger than the version of DOS supports ?

It is the CDROM and the other HDD. It was ok, then reinstalled Dos & Win98, now doesn't open other drive letters in Dos.

They are listed in BIOS.

Are you talking pure DOS, or MS-DOS mode from windows?
For the CD-ROM for pure DOS, the first step is getting it listed in BIOS which it sounds like you've done. Then you'll need to load a driver for the CD-ROM, something like MSCDEX

For the HD, was it autodetected in BIOS, or did you enter the cylinders, heads, etc manually? It's possibly mis-configured in BIOS

PureDos, Autodetected in BIOS.

Does the other HDD has partitions larger than 2GB? MS-DOS version up to 6.22 (and version 7.0 but I don't consider that pure DOS) usually doesn't support FAT32 partitions.

That would be the case, is 3GB 🙁

Ok so If I partition them in half using FAT, that will work then yea?

Thanks.

Yes, both partitions should be FAT16. The downside is that all the data that is currently on that HDD will be lost by doing this.