Bluescreen of Death During Startup

Windows may start loading up, but then suddenly stop, showing a Bluescreen of Death (BSOD). The error messages onscreen may or may not give a sound indication of the problem. These errors are deemed serious because access to a working operating system is limited because Windows will not start normally.

Failing disk
The first cause to be investigated is a failing hard disk because every passing moment that the disk is operating increases the risk of irreversible damage. Data recovery off of a mechanical hard disk is generally expensive in contrast to the modest cost of a backup solution. A failed hard disk can cause the following symptoms:


 * Blue screen of death at startup because the system cannot read from the disk.'
 * Hanging on Windows startup logo

Windows may boot very slowly or the BSOD may only occur sometimes but not always. You should look for signs of a failed hard disk:


 * If the failed hard disk is not the same one as Windows is installed onto, then disconnect the drive to see if the problem goes away.
 * Carefully listen for irregular clicking noises or a consistent rhythm that seems to stop after a few seconds (repeating)
 * Damaged hard drive units tend to become very hot quickly and may produce overheating symptoms.
 * if the disk is 3-5 years old and is performing abnormally loudly, it ought to be replaced even if Windows is loading successfully.

Utilities that check for hard disks faults may be unreliable. The only reliable method is to replace the drive with a known good drive. If the problem disappears then it can be narrowed down to a fault with the drive, the configuration or installed software.

Faulty memory
Faulty computer memory can cause BSODs, corrupt drivers and corrupted filesystems. After ruling out mechanical disk failure, computer memory should be checked to verify that it is not faulty, incompatible or failing due to some other hardware problem. The recommended program is memtest86 by Pass Mark. This utility is booted from a USB flash drive or DVD before Windows is started. It then checks the memory for faults. Please note that this may take hours to complete depending on the amount of installed physical memory. A detected fault does not necessarily indicate that the memory is physically faulty.


 * If a fault is detected then carefully remove all but one memory module to see if the fault clears.
 * If the fault persists, move that one memory module to another compatible slot (consult motherboard manual for more details).
 * If the fault clears, then it may indicate a particular slot is bad. If the fault persists, it may indicate that one memory module is bad. Then, swap it out with another module to narrow down the cause.

If you are not confident in carrying out these steps, get someone to help you or take it to a computer technician for a diagnosis.

Incorrect BIOS settings
The second cause to be investigated is if the BIOS is configured correctly. An incorrectly-configured BIOS may cause the infamous, "Inaccessible Boot Device" message. This tends to be caused by either a faulty hard disk (see above) or incorrect BIOS settings.


 * Check the BIOS to make sure the correct disk mode is set. If Windows was installed in RAID mode, then the BIOS should be set to RAID mode. If Windows was installed in AHCI mode, then Windows should be set to AHCI mode.
 * Check that there are no unusual emulation settings enabled. It might be good to reset the BIOS to startup defaults and then reconfigure each setting as required.
 * Test that the BIOS is holding any saved settings. Unplug the computer from the wall and test that the settings are being retained. If not, then replace with CMOS battery with a known good one.

Please note that BIOS settings can be changed without deliberate user intervention (such as a power failure). Therefore, the CMOS battery must be checked and replaced if deemed faulty.

Incorrect disk drivers
Complex configurations such as booting from a RAID or from an iSCSI requires drivers to be loaded and installed in Windows. Sometimes, Windows does not have the necessary drivers to be able to boot. Therefore, the user should download appropriate drivers from the motherboard manufacturer's website or from the iSCSI boot provider. When installing Windows, there is an option to select optional disk drivers which will be injected into Windows. Bad drivers may be a possible cause if:


 * The disk controller or motherboard in the computer was replaced.
 * The contents of the hard disk (including Windows) was transferred to a new system with different hardware (e.g. plugging the drive into a new computer or cloning the drive's contents to a new computer).
 * Required drivers were uninstalled (e.g. Windows update may replace drivers). Try rolling back Windows update to see if it solves the problem.
 * Drivers were corrupted or deleted. Try booting into safe mode to see if the problem goes away. If there is success booting into safe mode, then you should remove the bad drivers and install known working drivers.

Filesystem corruption
Filesystem corruption occurs when entries in the filesystem are incomplete or reflect inaccurate information about how data is stored. The file entries might be sound but references can be out of date. Typically, new information was not written because of a previous failure. NTFS uses journalling to keep a record of the old information and this data can be used to restore consistency to the filesystem. In extreme cases, filesystem corruption can prevent Windows from booting. BSODs may cause filesystem corruption by interrupting Windows before all data has been saved.

Filesystem Repair
Windows includes a free chkdsk tool that can be used to scan for filesystem corruption and make necessary corrections. Windows startup repair may automate this step automatically but Windows does not always detect the corruption. The tool can be started manually from a command prompt. You can access a command prompt from the Windows Recovery Environment (WinRE). Therefore, it is advised to setup a Windows recovery partition.

2. Locate Windows drive

 * You first need to locate the drive containing your Windows folder. In a recovery environment, it is rarely drive C:
 * It tends to be D or E under a recovery environment. Open a command prompt and type D followed by a colon (e.g. D:). Then type dir and locate the Windows folder.
 * Repeat previous step for each drive until the Windows folder is found.

3. Run chkdsk to correct potential filesystem corruption
Type chkdsk driveLetterHere: /f. Change driveLetterHere to the drive you located in step 2.'''4. Restart your computer and verify that the problem is solved'''

Once the repair is complete, you can reboot the system and try again.