Assuming you mean that your preferred search engine has been changed and you have uninstalled a program but you are still stuck with the change.
I would suggest that you download MalwareBytes.
Do a scan of the computer.
Before you agree to remove what it finds, turn off system restore - some nasties will reinstall themselves from system restore next time you restart.
Now remove the nasties, restart, scan again then turn back on system restore.
You may need to reset your search page manually.