@foone hey hey do you know the answer to this?
@shanselman @foone I don’t think it actually created a separate partition. It would compress all the contents of the drive into one big file on the C: drive’s root directory, and then kind of mount that file as the C drive on boot.
@shanselman @foone it’s possible @polpo has encountered this in some of his retro restorations
@shanselman @foone I don’t know more than what you shared there. But recently a few of us grey beards were discussing disk doublers and how they often made systems faster because storage was so much slower than compute that decompression was faster than reading from disk. The 20somethings looked at us like they thought we might be totally bullshitting them. I can’t blame them, it sounds nuts.

@shanselman @foone if it’s compressed it’ll have a utility to show you compression stats, like DBLSPACE.EXE. So I’d run that. But not necessarily anything in config.sys because dblspace.bin loads earlier. Mem will also show the driver chewing up RAM.

Or you could image it and try and mount the image on Linux.

@shanselman @foone this sent me to a trip down memory doubler lane. Here‘s an interesting article i found: https://tedium.co/2018/09/04/disk-compression-stacker-doublespace-history/ . Doesn‘t answer your question but has some neat insights.
Disk Compressor History: A Microsoft Antitrust Prelude

How a court battle involving groundbreaking disk-compression software foreshadowed Microsoft’s status as an antitrust darling.

Tedium: The Dull Side of the Internet.
@shanselman you'll see a drive with only one visible file: command.com. There'll be a couple hidden/system files: drvspace.bin/.000/.ini.
Not super obvious, to be honest.

@shanselman @foone

If you would boot an old MS-DOS computer and the filesystem was still working it would not matter since you would just see all the boot messages flash over the screen and it would just work as it used to. Most of the compression packages just created a hidden system file that was loaded as a virtual file system.

@shanselman @foone

Answering the second question. Yes, the device drivers would all be listed in the config.sys.