Hi all.

I have a very old system that only runs DOS.

My problem is that when I switch it on, it detects the hdd and goes through the startup sequence till just after the block with all your AMIBIOS system config.
It then says:
133MHz CPU
256KB External Cache Memory

This is where it gets stuck for about a minute or so, then REBOOTS and follows the same steps.

When I boot with a bootable disk, I can access my hdd. My autoexec.bat and config.sys files seem 100% correct.

I checked for the himem.sys file and it is there and intact. I've tried renaming it and copied a new himem.sys for my bootdisk to the hdd. This also id not work.

The only other thing that I can think is that my config.sys or COMMAND.com does not run.

So finally my question:
I know that when config.sys runs, there is a command line that causes himem.sys to run. I also know that any program you want to have start automatically, you can add the appropriate command line to autoexec.bat.
How does config.sys know when to run? Is there another file that runs first, with a command line for config.sys to start? Could it be that this file is the one that is corrupt?

Any help would be greatly appreciated!!
The DOS boot process for a hard drive is as follows. The first sector of the hard drive contains a special section called the "master boot record" or MBR for short. This contains a machine code program for booting the OS.

1. The BIOS, having COMPLETED its functions, loads the boot code in the MBR and transfers control to it. The master boot record code begins execution.

2. The master boot code examines the master partition table. It is searching for two things. First, it must determine if there is an extended DOS partition. Second, it must determine if there is a bootable partition specified in the partition table.

3. If the master boot code finds an extended partition on the disk, it loads the extended partition table that describes the first logical volume in the extended partition. This extended partition table is examined to see if it points to another extended partition table. If it does, then that table contains information about the second logical volume in the extended partition, so it is loaded and examined. (Recall that logical volumes in the extended partition have their extended partition table chained one to the next.) This process is CONTINUED until all of the extended partitions have been loaded and recognized by the system.

4. After loading the extended partition information (if any), the code attempts to boot the primary partition that is marked active (bootable). If there are no partitions marked active, then the boot process will terminate with an error.

5. If there is a primary partition marked active, the code will boot it.

6. The volume boot sector is loaded into memory and tested, and the boot code (more machine code) that it contains is given control of the remainder of the boot process.

7. The volume boot code examines the structures on the disk that it is booting to ensure that everything is correct and in the right place. If not, the boot process will end in an error here as well.

8. The code searches the root directory of the device being booted for the operating system files that contain the operating system. For a system running MS-DOS these are the files "IO.SYS", "MSDOS.SYS" and "COMMAND.COM".

(IO.SYS and MSDOS.SYS are usually hidden)

9. If the operating system files are not found, the boot program will display an error message, which is usually something like "Non-system disk or disk error - Replace and press any key when ready".

10. If the operating system files are found, the boot program will load them into memory and transfer control to them. First, IO.SYS is loaded and its code executed. IO.SYS will then execute MSDOS.SYS. Then the more complete operating system code loads and initializes the rest of the operating system structures. For MS-DOS, this means loading the command interpreter (COMMAND.COM) and then reading and interpreting the contents of the CONFIG.SYS and AUTOEXEC.BAT system control files.

11. At this point, finally, the operating system code itself has control of the PC.

So you can see that config.sys and autoexec.bat are dealt with right at the end.

It is possible that the MBR or VBR are damaged, and that you need to reinstall them.

You can try doing this by booting from your boot disk and typing

SYS c:

at the prompt, (if you have sys.com on the bootable disk. If you do not, but you have it on the hard drive, log into the folder where it is located e.g. if it is in c:\dos type c: then cd DOS and finally sys c:

Thank you very much!!

I've tried sys c: and it worked perfectly!

THANKS again, I had sleepless nights over this stupid problem.