Just because even I forget from time to time.
You need to do this as administrator, even better if the disk doesn’t have a drive letter or mounted in any way under Windows.
In my case I picked up a 486SX with an aging Fujitsu disk.
qemu-img.exe convert -f raw -O qcow2 \\.\PhysicalDrive2 fujitsu_MPB3021AT.qcow2
And as fast as your machine can read the disk, you’ll have your Qcow2 disk image. As of Qemu 2.9.0 the formats include:
Which is quite a list. Obviously since I’m reading a physical disk, the format is RAW. I just output it to Qemu for my personal ease.
Also once the image was created I could quickly run it under Qemu, and discover that yes this was a machine running Windows 95.
qemu-system-i386.exe -hda fujitsu_MPB3021AT.qcow2 -soundhw es1370 -vga cirrus