Windows - boot process & simple troubleshooting

[Paul Adams]

This is the (simplified) boot sequence for Windows NT, 2000, XP and 2003:

BIOS: performs Power On Self Test (POST)
BIOS: loads MBR from the boot device specified/selected by the BIOS

MBR: contains a small amount of code that reads the partition table, the first partition marked as active is determined to be the system volume
MBR: loads the boot sector from the system volume

BOOT SECTOR: reads the root directory of the system volume at loads NTLDR

NTLDR: reads BOOT.INI from the system volume to determine the boot drive (presenting a menu if more than 1 entry is defined)
NTLDR: loads and executes NTDETECT.COM from the system volume to perform BIOS hardware detection
NTLDR: loads NTOSKRNL.EXE, HAL.DLL, BOOTVID.DLL (and KDCOM.DLL for XP upwards) from the boot (Windows) volume
NTLDR: loads \WINDOWS\SYSTEM32\CONFIG\SYSTEM which becomes the system hive HKEY_LOCAL_MACHINE\System
NTLDR: loads drivers flagged as "boot" defined in the system hive, then passes control to NTOSKRNL.EXE

NTOSKRNL.EXE: brings up the loading splash screen and initializes the kernel subsystem
NTOSKRNL.EXE: starts the boot-start drivers and then loads & starts the system-start drivers
NTOSKRNL.EXE: creates the Session Manager process (SMSS.EXE)

SMSS.EXE: runs any programs specified in BootExecute (e.g. AUTOCHK, the native API version of CHKDSK)
SMSS.EXE: processes any delayed move/rename operations from hotfixes/service packs replacing in-use system files
SMSS.EXE: initializes the paging file(s) and the remaining registry hives
** before this step completes, bugchecks will not result in a memory dump as we need a working page file on the boot (Windows) volume **
SMSS.EXE: starts the kernel-mode portion of the Win32 subsystem (WIN32K.SYS)
SMSS.EXE: starts the user-mode portion of the Win32 subsystem (CSRSS.EXE)
SMSS.EXE: starts WINLOGON.EXE

WINLOGON.EXE: starts the Local Security Authority (LSASS.EXE)
WINLOGON.EXE: loads the Graphical User Identification and Authentication DLL (MSGINA.DLL by default)
WINLOGON.EXE: displays the logon window
WINLOGON.EXE: starts the services controller (SERVICES.EXE)
** at this point users can logon **

SERVICES.EXE: starts all services markes as automatic

---------

NOTES:
The SYSTEM volume is the partition from which the boot process starts, containing the MBR, boot sector, NTLDR, NTDETECT.COM & BOOT.INI

The BOOT volume is the partition which contains the Windows folder - this can be a logical partition

---------

Example 1:
2 hard disks, 0 and 1
Disk 0, partition 0 is the SYSTEM volume
Windows is installed to "D:" which is disk 1, partition 0 [even if disk 0 has an extended & logical partitions] - this is the BOOT volume
- if either disk fails or is removed, Windows cannot boot


Example 2:
1 hard disk, 2 partitions
Disk 0, partition 0 is the SYSTEM volume
Disk 0, partition 1 is the BOOT volume [D:]
- add another disk to the system and create a partition on it, this becomes D: and Windows will not boot [disk 0, partition 1 now becomes E:]

---------

Boot problems and their possible causes & resolutions:

Symptoms:
Black screen
"Invalid Partition Table"
"Error loading operating system"
"Missing operating system"

Cause:
Corrupt Master Boot Record (MBR)

Resolution:
Boot into Recovery Console and run "fixmbr" to repair the MBR

--

Symptoms:
"A disk read error occurred"
"NTLDR is missing"
"NTLDR is compressed"

Cause:
Corrupt boot sector

Resolution:
Boot into Recovery Console and run "fixboot" to repair the boot sector

--

Symptoms:
"BOOT.INI is missing or corrupt"
"Boot device inaccessible"
"Windows could not start because the following file is missing or corrupt:
<Windows root>\system32\hal.dll"

Cause:
BOOT.INI missing, corrupt or out of date as a partition has been inserted

Resolution:
Boot into Recovery Console and run "bootcfg /rebuild" to repair the BOOT.INI

--

Symptoms:
"Windows could not start not start because the following file is missing or corrupt:
\WINDOWS\SYSTEM32\CONFIG\SYSTEM"

Cause:
Corrupt/missing system hive

Resolution:
1. Boot into Recovery Console and run "chkdsk C: /f" to check the system disk for errors and fix them, then reboot.
2. If the error continues and System Restore is enabled, copy the system hive from the last restore point into \WINDOWS\SYSTEM32\CONFIG
3. If the error continues, copy the system hive from \WINDOWS\REPAIR into \WINDOWS\SYSTEM32\CONFIG
4. If the error continues, perform a repair installation by booting from the Windows installation media

--

Symptoms:
"Windows could not start because of a computer disk hardware configuration problem.
Could not read from the selected boot disk, Check boot path and disk hardware."

Cause:
Boot volume (with Windows folder) is not accessible as defined in BOOT.INI

Resolution:
Check the boot volume is accessible

--

Symptoms:
Dual-boot 32-bit Windows and 64-bit Windows system reports "NTOSKRNL.EXE is corrupt" trying to boot into 64-bit Windows

Cause:
System volume contains an older boot loader than the boot volume requires - e.g. XP SP2 installed after XP x64

Resolution:
Copy NTDETECT.COM and NTLDR from XP x64 installation media to the root of the system volume

---------

Notes:
Not all of the above applies to Windows Vista/Longhorn, there are a few differences:

- the boot loader is different, and if the machine has a TPM 1.2 chip then BitLocker might be involved right at the start to decrypt & validate the boot code

- the boot drive will become "C:" regardless of which partition it might be (so any bootable Vista volume will refer to itself as C: even in a multi-boot environment)

- WINLOGON.EXE no longer launches SERVICES.EXE, this is handled by a separate process WININIT.EXE, as session 0 is now solely the system area and not combined with the console desktop (the first interactive logon session becomes session 1)

- the recovery options are more automated via wizards by booting from the installation DVD, common faults can be checked for automatically

[MSIC]

Nice one mate. Potentially very useful indeed - have never been too hot with Windows Recovery Console.

[directhex]

so correct me if i'm wrong...


but if you mark a linux partition (which has a grub or lilo boot sector on it) as active, then wouldn't a windows MBR load it?

[wmsteele]

This could have helped me so many times in the past. Will be saving/printing this for future reference.

[Paul Adams]

if you mark a linux partition (which has a grub or lilo boot sector on it) as active, then wouldn't a windows MBR load it?

Short answer - no idea
Bear in mind that I haven't fiddled with OS's other than Windows for a good few years (XENIX, OS/2, OS/2 Warp, Linux) and this kind of stuff with the boot process (at this level of detail) is relatively new to me.

The MBR might expect the boot sector to be in a particular format, which in turn is hard-coded to look for NTLDR.
I know the boot sector is different for Vista as it tries to load BOOTMGR instead, but I'm not sure of the relationship between MBR and boot sector.
(Conversely, the MSDOS boot sector looks for MSDOS.SYS & IO.SYS IIRC.)

The MBR, boot sector and boot files on the system volume are typically bundled together when it comes to troubleshooting, as most installations are basic singe-volume, single-OS.

Edit:
Found this page detailing the NT 5.0/5.1 MBR which lists the requirements for the MBR to load an OS from a partition as:
1) it is on the Primary Master hard drive
2) it is set to be the only active partition
3) it has a boot loader in the first sector of that partition

Not sure about the first point as SATA disks as I don't think there is such a thing as a master SATA disk... and it's possibly up to the BIOS to determine the order of scanning devices on the PATA and SATA buses, so may be unpredictable...

[aidanjt]

Well the MBR loads a small portion of boot sector code, whatever code is in the boot sector loads whatever boot manager is installed there (I'm sure this is how it works).. But I just avoid this issue altogether by installing GRUB to the MBR and let it chainload windows, works a charm.

[8bit]

As I understand it, the Windows bootloader *can* be configured to boot a Linux, although I've never seen it done. I guess it would require some very specific knowledge on the subject.

I think this thread should be made a sticky, thanks Paul that's going to help me a lot the next time i get me bootloaders in a twist!

[directhex]

As I understand it, the Windows bootloader *can* be configured to boot a Linux, although I've never seen it done. I guess it would require some very specific knowledge on the subject.

I think this thread should be made a sticky, thanks Paul that's going to help me a lot the next time i get me bootloaders in a twist!

ntldr can be convinced to do it (i made it boot beos once), but the question is more about the windows MBR, which happens *before* ntldr

[black_13]

What displays the boot splash in vista (and how do i make it go away)
thanks
black_13

[directhex]

assuming it's the same as xp, the splash is embedded in the kernel

[Paul Adams]

What displays the boot splash in vista...

winload.exe (the boot loader) has the code to display the black screen with the animated bar which is used by default, and the localized version (winload.exe.mui) contains the alternative boot screen (as it contains text which is language-specific).

...(and how do i make it go away)

If you use the NOGUI option then a static 24-bit colour imge stored inside winload.exe is used instead.

To enable NOGUI:
- Run MSCONFIG
- Select the Boot tab
- Check the "No GUI boot" box
- Reboot

This is your loading screen now:



[Pre-empting the next question of "how can I use my own image during startup?"]
As with previous versions of Windows, to replace this image with a custom one involves hacking the EXE file to embed the image, which on Vista involves taking ownership of the file first due to the extra security in this version of the OS.

It has always been a risky proposition to go resource hacking, but lots of people do it, and there is a tool someone has developed to embed custom images for you in the x86 version:
Development Dan’s Blog » Blog Archive » Windows Vista Boot Logo Generator Beta
I have not used this tool and cannot vouch for it, use at your own risk.

[black_13]

thanks for the response.
actually i would prefer to no resource hack but find out if there is a registry setting or some legitimate hook that would allow me to do what i want. but your info gives me a start point.

i will update you on what i find.
black_13

[directhex]

thanks for the response.
actually i would prefer to no resource hack but find out if there is a registry setting or some legitimate hook that would allow me to do what i want. but your info gives me a start point.

i will update you on what i find.
black_13

the registry is a million miles from loaded when the splash screen is appearing. and do you really want an OS where you can hook into the kernel before it boots - that doesn't smell like virus activity to you?

[mahzad]

how can write commmand in my own bootloader?
i want to run a code to access pagefile.sys so before windows is booted i can access this file!
do you have any idea to access pagefile ?
i wan to write bootloader !but i donot know anything?

[aidanjt]

Just boot another OS off a USB stick or something.

[lodore]

i have chainloaded grub using the vista bootloader using a program called easybcd.

btw very interesting thread i will read about the windows boot process when i have time