If only one floppy drive is present on a Microsoft Windows guest and the isa-fdc.driveB property is set, the following error message can appear when attempting to access the drive:
A:\ is not accessible.
The floppy disk controller returned inconsistent results in its registers.
This problem only occurs when using the QEMU command line directly, which is not supported. To work around this problem, specify the isa-fdc.driveA property when using a single floppy drive.