Can the sewing machine itself format the disk? If it can, use it to format the disk. If not, you're only solution is to keep trying different floppies until you find one the D1 likes. Floppy disk quality got worse & worse in the late 90's. I had to dig through my husband's old stuff to find older disks from the 80's to make boot disks for some computers we used to support. I've had to format disks with certain brands of floppy drives for certain brands to read. Also try blowing the dust out of your computer & D1. Sometimes a little bit of fuzz can cause major problems.