On Wed, 17 Sep 2003, Tillman, Edward wrote: Other than AFTER-MARKET add-ons, the only versions of MS-DOS that I have seen that support 8" disks were SB-86 v 1.x (a rare version of MS-DOS distributed on 8" by Lifeboat), NEC APC and 9801, and some OEM versions of MS-DOS 1.25, 2.11 and 3.31. (those were the versions of MS-DOS that actively supported customization) 'course you COULD use 8" DSDD from MS-DOS AND PC-DOS 3.00 on by lying to it and calling your 8" drive a 5.25" 1.2M. That will identify which MS-DOS format a given disk has on it. HIS disks will resond with "Probable Non-DOS Disk", "Sector Not Found", "Address Mark Not Found", or "General Failure", since they are presumably NOT MS-DOS formatted. "Probable Non-DOS Disk" means that it is MFM with 512 bytes per sector, but does not have valid MS-DOS structures found on it. "Sector Not Found" means that it is MFM, but the sectors are not 512 bytes, or not numbered the way MS-DOS expects them to be ("there ain't no sector #1!") "Address Mark Not Found" usually means that it is NOT MFM (such as unformatted, GCR, FM, etc.), or is MFM at a density that is not recognized. "General Failure" means "none of the above". An error that wasn't successfully identified. Contrary to popular belief, it was NOT a reference to Nam. Most of the better manufacturers put that info on the label. With unlabelled 8" diskettes, look at the index hole position. With unlabelled 5.25" disks, the only thing that could be readily determined was a difference in color between the media of "HD" v LD; and if whether there was a hub reinforcer (not present on early SD and on HD unless added by the user) I have never seen an 8" diskette with a spring loaded media cover. MANY manufacturers of 3.5" diskettes did NOT mark the disk. (Shall we get into the "PINCH" arrow?) Later model 8" disks are often marked. If not, the index hole position identifies whether it is single or double SIDED. Being rated for single v double DENSITY was an issue of "fidelity", and not visible unless marked.