I have Nvidia GT750M in a laptop, with "display GPU activity icon in notification area" activated. Right now all I have open are Google Chrome, Notepad++, and windows explorer, yet it says 2 processes are using the GPU. How do I find out WHICH processes are using the GPU? Without installing extra software.
You can use tool Sysinternals Process Explorer. You can download it from Microsoft website. https://docs.microsoft.com/en-us/sysinternals/downloads/process-explorer It kind of is extra software, but you download it from Microsoft website, not from some unknown company website. So it's more like extra update form windows. :)
After you run it go to "view -> select columns -> Process GPU" and check "GPU Usage".