EXTMINOOOP is a pretty popular virus.
You can get it on your computer while downloading it bundled with some free software.
Sadly, most free downloads do not disclose that other programs will be installed, so you are more likely to get EXTMINOOOP on your PC without your own knowledge.

After being downloaded, EXTMINOOOP hijacks your browser and changes search settings.
EXTMINOOOP also causes an appearance of popup ads and browser redirecting.

EXTMINOOOP is very annoying and hard to get rid of.
Make a full backup of your PC before starting.
Follow the next steps to make your system clean again:

Removal guide for EXTMINOOOP:

1. Uninstall EXTMINOOOP using Windows uninstallation applet (use Add/Remove Programs or Uninstall Program or Apps & features).
2. Open Task Manager and terminate "EXTMINOOOP" processes.
3. Use Windows search to find and remove "EXTMINOOOP" files and folders.
4. Run services.msc and disable a "EXTMINOOOP" Windows service.
5. Execute taskschd.msc to get rid of "EXTMINOOOP" scheduled tasks.
6. Open regedit.exe and delete EXTMINOOOP registry keys and values.
7. Inspect the properties of your desktop and Start menu shortcuts for EXTMINOOOP presence and "http://" links.
8. Open your browser and disable EXTMINOOOP plugins. Disable all unknown plugins. Reset the browser settings.
9. Clean your Recycle bin and temporary files.
10. Restart your computer and check results.