Hi Fred I tried 22DISK for my M20 but it didn't work. The tables were wrong, as well as that my computer didn't deal with single density. Since it had no way of ignoring track 0, easily, I gave up on it. I found that the single density, on track zero, was solved by using the M20 to pre-format the disk and then used my routines to write the double density stuff to the remaining tracks. If Geoff has the same issue, he might be able to deal with the single density the same way. I found that the first track being single density was just a boot compatability issue. The first track would just have enough code to switch to double density and then the main loader was on track 1. This meant that the code was basically the same on all of the track zero's. I'd forgotten that the BIOS wouldn't deal with the single density. I was thinking more in terms of number and size of sectors. Dwight