Did you install software recently?
Remove it and try to detect the flashing DOS window again.
- If you do not see this flashing window anymore, it is safe to assume that this software was the culprit. And you should investigate what that latest piece of software is doing in the background. And find alternatives for this piece of software.
- If you keep seeing the flashing DOS window, repeat the step above with the latest software you installed -1
This is the 'elimination' process.
Or you can use:
Those will kill whatever your antivirus software and/or anti-malware software miss.