Diagnosis And Repair - Part 1
Windows is just so expansive, to deal with every error would take months and more web page space than I have.
The Boot Sequence
Part of your Diagnosis and Repair questioning will deal with the boot sequence. As a refresher, here is the boot sequence for both DOS and Windows;
DOS Boot Sequence
- The computer scans for a Master Boot Record on either Drive C: or A:, depending on which drive is present and the order set in the CMOS.
- The Master Boot Record (MBR) and DOS Boot Record (DBR) is loaded. The MBR loads if booting is occurring from a hard drive, and is followed by the DBR. The DBR only loads if booting is occurring from a floppy. Once the boot record is loaded, the boot partition is located.
- The DBR loads IO.SYS and MSDOS.SYS. IO.SYS loads CONFIG.SYS.
- COMMAND.COM loads. COMMAND.COM then loads AUTOEXEC.BAT.
- COMMAND.COM displays the command interface.
Windows 3.x Boot Sequence
The Windows 3.x Operating System technically does not boot on it's own. It uses the DOS boot sequence because it runs from a command inserted in AUTOEXEC.BAT called WIN.COM. Windows 3.x can NOT run without a prior DOS installation because of it's dependence on DOS.
Windows 9x Boot Sequence
- The POST is run by the BIOS.
- All Plug-And-Play devices are configured by the BIOS.
- The partition table is loaded, and the boot record initiates IO.SYS. The Real Mode section of the boot begins.
- MSDOS.SYS initiates any Windows 9x boot paramaters, including Multi-Boot.
- If file compression is present, DRVSPACE.BIN loads.
- SYSTEM.DAT is checked, and when validated loads the registry.
- The computer is scanned for new hardware. Any new hardware is identified and the computer looks for drivers for that equipment.
- If CONFIG.SYS or AUTOEXEC.BAT have any instructions in them, they are initiated by IO.SYS. Real mode ends and Protected mode begins.
- WIN.COM loads. All virtual device drivers and Virtual Memory Drivers are loaded, including SYSTEM.INI and VMM32.VXD.
- The GUI, Kernel, and User interfaces are loaded. Internet Explorer begins, and network support is loaded.
- Any files with a RunOnce registry key are loaded.
- Any files in the Startup registry key are loaded.
Boot Error Messages
You'll need to know some of the basic boot error messages. DOS errors are fairly easy to deduce, as Microsoft hadn't realized how useless they could make their messages yet. When Windows 3.x came around, the messages got longer and less useful. By the time Windows 95 came around, error messages required a secret decoder ring to figure out. None the less, you are required to know these basic errors.
| Error Message | Problem | Solution |
|
DOS Errors | ||
| Missing Operating System | The master boot record can not find the boot partition. Either the operating system is missing, the hard drive is damaged, or IO.SYS is missing. | Try copying
IO.SYS from a computer with the exact same DOS version
to the root directory of the boot partition.
(You'll need a boot disk.)
Ensure the hard drive is installed properly and the operating system is present. (You may need a boot disk for this as well) Format the drive and re-install the DOS operating system. |
| Non-System Disk Error | There is a floppy disk in Drive A:, or part of your Windows installation is corrupt. | Remove any
floppies in the disk drives.
Check to make sure IO.SYS, MSDOS.SYS, and COMMAND.COM are present on the hard drive. (You'll need a boot disk again.) |
| Bad or Missing COMMAND.COM | COMMAND.COM is either corrupt or missing. | Copy COMMAND.COM from a boot disk or another computer with the same version of DOS to the root directory. |
| Incorrect DOS Version | The version of COMMAND.COM installed on the computer is not the same DOS revision as the rest of the DOS files installed. | Same As Above. If not copy of COMMAND.COM is available, re-install DOS. |
| Error In CONFIG.SYS/Bad Or Missing Driver.DRV | The error will quote a line number that has either an incorrect command or an invalid directory. | Check the line
number or Driver file listed. Ensure the file is
present, and that the command calling that file is
correct.
Replace the file if the above doesn't work, as the file is probably corrupt. |
| Windows 3.x Boot Errors | ||
| A Device Referenced In WIN.INI Could Not Be Found. | A file or device listed in the WIN.INI system file is not present or can't be found. | If the device
listed is no longer present, edit WIN.INI and remove the
reference.
If the device is still there, remove the reference in WIN.INI and re-install the device drivers. |
| SwapFile Errors | Either your swap file is corrupt or has run out of hard drive space. | Clean up your
hard drive to allow more space for Virtual Memory.
Us the Control Panel's Virtual Memory system inside Enhanced Mode to reestablish a new swap file. |
| HIMEM.SYS Not Loaded | Either HIMEM.SYS isn't present or wasn't loaded in the CONFIG.SYS. | Make sure
HIMEM.SYS is present in the directory listed in the
CONFIG.SYS under "DEVICE=C:\<Directory Name>\"
Make sure the above CONFIG.SYS entry is present in the CONFIG.SYS. |
| Unable To Initiate Display Adaptor | Windows 3.x does not have a default adaptor setting for your video card. Your existing video card drivers have failed to initialize, so Windows is shutting down. | Re-load your video card device drivers. If this doesn't work, load the default VGA drivers. |
| Windows 9x | ||
| General Protection Fault (GPF) Error in USER.EXE | The USER system area has run out of space to file data. | Change FILES=xx to FILES=100 in the CONFIG.SYS. |
| OE Exception Errors | The computer has detected bad memory. | Check your on-board memory for bad RAM. Ensure that your RAM timing in the BIOS is correct. |
| OD Exception Errors | There is a video error. | Check to make
sure your video card is functioning properly.
Make sure that the latest video drivers are running on your computer, and that they are right for your video card model. |
| Out Of Memory | The core components of Windows have run out of memory space. This is normally caused by programs not releasing their memory allocations after they are closed. | Reboot the
computer.
Add more RAM. |
| Windows Error Accessing System Registry | The Registry is corrupt. | Reboot in safe mode and replace the SYSTEM.DAT file with a backup copy of the Registry. (You'll need to set the SYSTEM.DAT file to ATTRIB -s -h -r to do this.) |
Quick Tricks For Diagnosing Boot Errors
There are some easy tricks to remember when diagnosing boot errors in both DOS and Windows. Here are a few;
- Most DOS boot errors are directory errors in CONFIG.SYS or AUTOEXEC.BAT. Always check to make sure you have the correct directory path and that the file name is correct. Also, make sure the file is present where you're telling the system to look for it.
- In DOS, use the PATH command to add functionality to the system. The PATH command allows COMMAND.COM to automatically load commands into the interpreter by simply listing the command in the PATH line. Adding the Windows directory to PATH can give you Windows setup capability within DOS.
- Most problems with loading Windows 3.x occur because of swap file problems. If possible, try to set up a permanent swap file of sufficient size to keep your system running.
- If you can't load Windows 9x, press F8 when the "Starting Windows 9x" line shows up after the POST. Choose Step-By-Step Confirmation. This will ask you before loading any file, and can help you isolate a problem that Windows is not giving you an error for. (This happens ALL the time.)
- If you want to see where a Windows 9x boot is failing, check the BOOTLOG.TXT file. You also can boot in Safe Mode using the same F8 command as #4 to boot the system with minimal drivers and no network support.
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