DOS (including FreeDOS) tends not to behave too well on systems without any floppy drives: it may reserve drive letters A: and B: regardless, and return errors when they are actually accessed. And even though your computer has no floppy drive, the BIOS firmware may still report one as being present, for example in order to support installing a floppy drive in a hot-swappable extension bay like in some Dell laptops.

Most importantly though, when a second floppy drive is not present, DOS enables its second drive emulation feature. It simply makes the single floppy drive available under *both* A: and B: drive letters, and prompts the user to swap floppies when the program attempts to access files on the ‘other’ drive. Though I cannot explain what made installer access the B: drive, this feature is what triggers the message displayed in your screenshot.

As for solutions, I can offer one: disable both floppy drive letters before running the installer.

Ensure you have the DEBUG program ready on your USB stick (any version; Microsoft’s, as you may extract from Windows 98 CAB files, [FreeDOS’s](https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.2/repos/base/debug.zip) or [ecm’s](https://pushbx.org/ecm/download/ldebug/)). Before starting the installer, launch DEBUG and type the following at the `-` prompt:

```
a 100
; disable drive A:
mov ax, 5f08
mov dl, 0
int 21
; disable drive B:
mov ax, 5f08
mov dl, 1
int 21
; exit
mov ax, 4c00
int 21

rcx
13
n nofdd.com
w
q
```

The blank line before `rcx` is important, but you can skip those starting with a semicolon. The above creates a small program named NOFDD.COM which disables floppy drive letters A: and B: and makes them unavailable until the next reboot. (If you skip the first section, it will disable the B: drive only.) You can invoke it directly by starting `NOFDD` the command line, or put in in AUTOEXEC.BAT or in an `INSTALL=` directive in CONFIG.SYS.

Having ran `NOFDD` (you can check that switching to drive A: or B: no longer works), launch the installer as before; one should hope the above will get you through this particular hurdle, or at least give you a more informative error message.

Note that the installation process involves a number of reboots from the target medium. Since Windows 98 has no built-in drivers for USB drives, this means you may lose access to the installation files on the USB drive after the reboot, unless you take additional steps, like copying CAB files onto the target partition, or even installing DOS USB drivers (FreeDOS does come with those).

Beware also of drive letters shifting between reboots: when booting from a USB flash drive, BIOS firmware often presents it as hard drive number 0 (0x80) while actual internal hard drives are numbered starting from 1 (0x81), but when booting from an internal hard drive, those are numbered starting from 0, while USB drives are hidden. This may disrupt DOS’s drive letter assignment algorithm and invalidate any pathnames the installer may have written in the target system’s configuration.

For these reasons, it is probably better to copy installation files onto the target partition and always boot from the latter.