How the system boots up
1:02 AM | Author: Harpreet Singh Khandiyal


Once the machine is powered on, it goes through a POST (Power-On Self-Test) sequence. The POST sequence displays information about the BIOS, and the amount of memory installed. The system will also attempt to initialize PCI cards. Once the POST sequence has completed, one can then see a basic table outlining the system configuration including disk information, and PCI card information.


The system goes through the process of acquiring a DHCP address, normally referred to as DORA:
DHCP (D)iscover
DHCP (O)ffer
DHCP (R)equest
DCHP (A)cknowledge
If the system is able to acquire an IP Address successfully, then the networking configuration settings are populated, such as Default Gateway, DNS Servers, WINS servers and so on.
If the system is not able to acquire an IP Address, then the system will time out / fail trying to process various networking functions - including the application of group policies and even possibly logging on to the client machine.


Let’s assume that the system has received an IP address from the DHCP server, now the DHCP Client service will try to register its IP Address with the DNS Server


The system attempts to query DNS for a SRV record for a Domain Controller. If the system locates a domain controller it then begins the process of applying system-level domain and group policies.
If no DC can be located, then we are in another timeout situation where group policies will fail to apply.


Once the computer settings are applied, the user logon prompt is displayed and the user enters their credentials


If the system was able to contact a domain controller, then the logon is authenticated and user policies are applied. If the system was not able to contact a domain controller, the system may log the user in with cached credentials. Since no domain controller could be located, user GPO’s will not be applied.

Troubleshooting Boot-up Issues:

If there is any issues while booting the system, you can to boot the computer in a "Clean Boot" Mode and check if the issue still persists:

For a clean boot, please try these steps:
-Click on start, then click on run (if run is not available, incase of Windows Vista, then type run, in the start search box and hit enter).
-On the run window type "msconfig" (without quotes)
-Click on services tab, click on "hide all microsoft services", now click on disable all
-Click on startup tab, click on disable all
-Click on OK and restart the computer

One can also try to boot the computer in Windows Safe Mode, to diagnose the issue, to boot the computer in safe mode, While booting the computer keep tapping the "F8" key on the keyboard, till you see "Advanced Boot Options" and then using the arrow keys highlight "Windows Safe Mode" and then hit Enter.
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