This problem was happening more when i was playing games that uses a bit more of the video card, like PUBG or Overwatch, but lately is starting to happen sometimes even when im browsing online.
Unfortunately, it seems that you're using an illegally activated copy of Windows which is against our forum rules. For us to assist you, you will need to ensure that you have a legal copy of Windows installed. I would thoroughly recommend that you upgrade from Windows 7 anyhow, since the operating system is no longer supported by Microsoft.