Hi Geoff If it is done a track at a time, you can deal with it by using the low level disk access functions of the BIOS. You do have to have a disk controller that supports single density ( not all do ). There are a few articles around that describe setting up the DMA ( needed for floppies ) and the disk controller, as another option. I've found this method to sometimes be machine dependent so if you can get by with the standard BIOS calls, that is a better way. If you can read Forth, I can send you some code I wrote to write tracks for my Olivetti M20 ( Z8000 machine ). I don't have a controller that does track 0 that is single density but you can get the idea of how to handle the controller and DMA. The other tracks are double density ( 360K drives ). You also need a compatible drive. You can't use a 1.2M drive to write single density at all and double density is not properly done so it will most likely fail to read reliably( a track width issue ). It may also be that your machine is supported by things like 22DISK. Have you tried this? Dwight