If you got some problem in your computer and asked for help to the service provider, you need to provide the serial number for you computer which is also called service tag, by this they can track the logs of issue and the hardware of your computer.
For the loatop its very easy to find the service tag, which is in the base of laptop. For the desktop computer its somewhere in the back side of CPU. Its just the sticker with service tag stick on it. Some time its not visible properly or its not available there. Also the sticker that holds the service tag is often placed at a more harder-to-reach location.
So here is the simple way how you can know the serial number for your computer or service tag.
Just open the command prompt (Start –> CMD)
Type the following command:
wmic bios get serialnumber
There is also another command which show the serial number or tag with the model or make of your computers.
wmic csproduct get name, identifyingnumber
The system model number can also be found using the System Information program available under All Programs –> Accessories –> System Tools.
This commands should work on Windows 7, XP and Windows XP Pro machine as wmic.exe didn’t ship with the previous editions of Windows. Refer to this page to learn about all other system details that you can retrieve with the help of wmic.exe command.