tomf@cms2.UUCP (Tom Fortner) (05/02/90)
In article <10103@sdcc6.ucsd.edu> ir230@sdcc6.ucsd.edu (john wavrik) writes: > >When running CHKDSK I just started getting the error message: > > Probable non-DOS disk. > Continue (Y/N)? > John, You may have lost the archive bit on your FAT file, resulting in the probable non-Dos disk message you received. If this is true, low level format is the only way to restore the archive bit unless you can reconstruct the FAT file with PC Tools rebuild or the like. Tom -- Tom Fortner Christian Medical & Dental Society UUCP: cms2!tomf INTERNET: tomf@cms2.lonestar.org
BL.JPL@forsythe.stanford.edu (Jonathan Lavigne) (05/03/90)
In article <174@cms2.UUCP>, tomf@cms2.UUCP (Tom Fortner) writes: >In article <10103@sdcc6.ucsd.edu> ir230@sdcc6.ucsd.edu (john wavrik) writes: >> >>When running CHKDSK I just started getting the error message: >> >> Probable non-DOS disk. >> Continue (Y/N)? >> >John, > You may have lost the archive bit on your FAT file, resulting in the >probable non-Dos disk message you received. If this is true, low level format is the only way to restore the archive bit unless you can reconstruct the FAT >file with PC Tools rebuild or the like. You don't need to do a LOW-LEVEL format get rid of the "probable non-DOS disk" message. A DOS reformat will fix the problem -- at least it did for me when I was getting this message a few months ago. But, in fact, there are several other easier ways to fix the problem. Both Mace Utilities and version 6.0 of PC-Tools have utilities that make the necessary correction to the FAT for you. A couple of months ago, several people posted messages that explain how to correct the FAT yourself using earlier versions of PC-Tools or Norton or something similar. Here is an explanation someone on CompuServe sent me. ------------------------------------------ #: 45742 S1/DOS/DOS Utils [S] 18-Sep-89 19:08:32 Sb: #45388-Non-DOS Disk problem Fm: Dave Angel 71046,1567 To: Jonathan Lavigne 70436,1272 Your 'probable non-Dos disk' error is usually caused by the first two bytes of the FAT tables being trashed by some software. They don't matter much anymore, but it's a good thing to fix them, if only to keep CHKDSK happy. (On floppies, before 3.2, the first byte was called the FAT ID, and was used to decide whether the disk was single sided or double, etc. On hard disks, and more recently on floppies too, the information is listed in the more general BPB, contained in sector 0). The first FAT is in sector 1, and you can find the second FAT various ways. If you have Norton or equivalent, let it show you how. Anyway, the first two bytes should be F8FF on every hard disk I've seen. As always, be thoroughly backed up before experimenting like this. If you patch both copies, and if CHKDSK is happy, I'd call the operation a success.
cjp@beartrk.beartrack.com (CJ Pilzer) (05/03/90)
The error from CHKDSK "Probable non-DOS disk, Continue (Y/N)?" generally is not as serious as it sounds. There is a byte called the Media Descriptor Byte, located in the FAT. When this byte becomes corrupted, you get the non-DOS error. Do not use the /F parameter. If you have the Norton Disk Doctor in the Norton utilities, it can fix the byte. Since you need to ask the question you probably would not br comfortable in using a sector editor, but if you or a friend want to, check Sector 0, offset 21 of the Boot Record, Sector 1, offset 0 of the FAT 1, Offset 0 in the first sector of FAT 2. On a DOS hard disk this byte should be F8 hex. On other disks it would be different. F9 5.25 AT floppy, FF 5.25 2 sides, 40 tracks, and 8 sectors. FD 5.25 2sides 40 tracks 9 sectors, and so forth. There is a booklet which comes with the Norton Utilities which explains some of this and on page 108 describes a way to edit this byte. YOU DO NOT NEED TO REFORMAT YOUR DISK. PHEW! I hope this helps you. -- cj cjp@beartra.beartrack.com
ECONO@latvax8.lat.oz (05/03/90)
In article <174@cms2.UUCP>, tomf@cms2.UUCP (Tom Fortner) writes: > In article <10103@sdcc6.ucsd.edu> ir230@sdcc6.ucsd.edu (john wavrik) writes: >> >>When running CHKDSK I just started getting the error message: >> >> Probable non-DOS disk. >> Continue (Y/N)? >> ***************************************************************************** I had a similar experience. After getting some advice, I managed to fix the problem by using Norton's Utilities to check the FAT. The first value of the FAT should be the Hex value F8. Something had changed that, so I kept getting the "Probable non-Dos disk" message. Changing it back to F8 solved the problem without having to do a low level format. Good luck! Nils Olekalns