I have a 386 computer running 3.1 windows. I know it's old. I should throw it but...
When I boot it. It says the hard drive is a non-system disk replace and press any key.
It was working ok
I can get it running by using a dos boot disk.
Also I had a look at the autoexec.bat file. There is nothing in it.
the command.com file is all characters with no sence can not really read it. Also can not read the files on the bootdisk.
Please help thank you

If the hard drive controller has failed,the hard drive won't be recognised by the bios.This controller electronic circuit board is on the hard drive.To find out if the drive is defined correctly, enter the bios at start-up time by pressing Del or the keys indicated on the first screen while the computer is ticking the POST test.Normally you will find a user defined hard drive.You need to define heads, cylinders and sectors.The Wpcom and Lzone may be 0 if unavailable.If you think from what you see that the drive is bad,install a new one selecting the master jumper to get it to boot(SCSI drives have no jumpers and 50 pins vs 40 pins for the IDE or EIDE drives normally found).Your new drive may be a used unit of 500 Mo or less if you want to avoid having to use an overlay program(the install program from the manufacturer or the Ontrack disk manager you can find at the following address).The hard drive case has written on it the data you need to install a drive or you may go to a drive site to find them.
Drive data(hds,cy. and sect.):
http://www.thetechpage.com/cgi-bin/default.cgi
Disk manager(overlay):
http://www.doslife.com/stuff.html
If you feel the drive is good, use the boot disk to sys the drive and transfer the 3 system files to the hard drive to make it bootable:
sys C: (press enter)
Reboot the computer without the diskette.Re-install a dos system to correct the config.sys and autoexec.bat.
Good luck.

Switched on:

Your hard drive is working fine. In some way one, or some combination of the three core DOS files are missing or corrupt. Boot using a boot floppy using the same version of DOS that is on the hard drive and type "sys c:". That will reinstall command.com and the two other "hidden" operating system files. It is normal for command.com to look all jumbled up and not make any sense, as it is not written in ASCI format. I believe it is written in machine language.

The config.sys and autoexec.bat can be opened in a text editor like Wordpad for Windows or edit.com for Ms-dos to read the content.The lines can be corrected and saved but if the dos system is badly damaged the full re-install is a simple task to do.MS-DOS 6.22 has only 3 diskettes for the whole set. Same applies to the install set for Windows 3.1 with 7 diskettes including the printer drivers on the last two.It all depends on the damage the system has suffered before being useless.Good luck.

Thank you for replying to my message and helping me
I tryed the sys c: it come back that it was the wrong dos version
I will have to find some dos disc and reinstall dos.
thanks again

Try something called pts-dos 2000 (it's free)
it worked for me on my 386 running 3.1 and p120 running windows for workgroups (downgraded from crap '98