"your PC may have been exposed to a virus" unclosable screen

For anyone who is unable to open the run dialog or task manager because this popup just stays on top - restart your computer, right after you sign in before it’s done loading hit CTRL SHIFT ESC a few times. This will open task manager as soon as the desktop loads. Now you can search for the task PulseBrowser and hit the end task button a few times until they are all gone. If you are fast enough you can do all this before the popup opens and covers the screen.

Check your installed programs since in this case the computer had a few other sketchy browsers that were installed and remove those too.

Finally check chrome for the default home page being changed to a sketchy domain and revert that.