Windows keeps a record of the date your computer's manufacturer installed the operating system. As long as you haven't reinstalled Windows since you got the computer, this date corresponds to the computer's age, providing a way to check when your computer first turned on. If you have reinstalled Windows, there are other methods for finding out your computer's approximate age.
Check the Windows Installation Date
If Windows has only been installed once on your computer, finding the date it was installed tells you the approximate age of your computer. Press "Windows-R" and type "cmd" to open the Command Prompt and then type "systeminfo" and press "Enter." When the system is done listing information, scroll up and look for the Original Install Date line; that is when Windows was installed.
Check the Hardware
Some computer manufacturers include a sticker with the date of manufacture somewhere on the case. If you can't find a date, look for a serial number and contact the manufacturer to find the computer's history. Searching for the PC's model number on the manufacturer's website can narrow down the computer's age.
Check the BIOS
You can also get a rough idea of your computer's age based on the BIOS listed in the Device Manager. Click the Start button, type "system information" and choose System Information from the search results. With System Summary selected on the left, look for the BIOS Version/Date in the right pane. This date, which corresponds to the BIOS on the motherboard, precedes the computer's manufacture date, typically by less than a year.