How to find the serial number of remote a computers in your network.

copy past the following code in notepad and save in "*.vbs" file. then double on it, it will ask for computer name. just enter the name of computer in your network and it will show you its serial number.

==============================//////======================
On Error Resume Next
Dim strComputer
strComputer = InputBox("Enter the name of the computer:")
Set objWMIService = GetObject("winmgmts:" & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")
Set colSMBIOS = objWMIService.ExecQuery ("Select * from Win32_SystemEnclosure")
For Each objSMBIOS in colSMBIOS
MsgBox strComputer & ": " & objSMBIOS.SerialNumber
Next
===========///////================================///////=====

Or login remotely to that system and type the following command.

C:\Users\Administrator>wmic bios get serialnumber
 

who have changed the password of a user in AD

The following command will show that when the password has been changed

C:/>net user username

Then from above command you will know that when that user password has been changed.
then go to event viewer and security logs on your DC and check the events that are accord at that time, you will see the event ID=4724,

please note that Auditing will be already enabled in your AD environment.

How to export certificate from Domain controler

Use the the following command to generate certificate.

C:\>certutil -ca.cert certificatename.crt

you will find your generated certificate in C:\
please note that Active Directory Certificate Services will be installed on your Domain controller, you can change the certificate extension according to your requirements.

Free SSL certificate

https://ssl.comodo.com/free-ssl-certificate.php
https://www.instantssl.com/free-ssl-certificate.html

How to activate windows 8

Open command prompt with admin rights

Type the following command, it will show you that your window  8 is activated or not.
c:>slui.exe

If your window is not activated then type the following command with key.
slmgr.vbs -ipk <key>

Without "<>" please