It is possible to find out the date when your Windows 7 was installed using command prompt. Open Command Prompt by clicking Start button, typing “cmd” (without quotation marks) and then hitting Enter key from the keyboard. Command prompt will open, type:
wmic os get installdate
It will show date in Unix epoch time format (i.e. number of seconds since 1970-01-01 00:00:00 UTC). To convert it to “normal” date and time, type further:
systeminfo | find "Install Date"
Now, you will get the original date of installation of your copy of Windows 7: