There are many toolbars that include a malicious software with them and these malwares automatically change the default homepage on your browser. If you have installed any of these toolbar or addons like Delta search and you are not able to remove it, then you can use AdwCleaner to clean up your browser.
AdwCleaner: AdwCleaner is a free software that doesn’t require any installation. This software can be deployed on any storage device and you can run it on any PC. When you start AdwCleaner, it immediately finds all the unwanted components or remnants of any former installations, and you can perform various actions (clean/uninstall) on them.
You can also use Avast Antivirus to clean up malicious software from you PC. The new Avast Antivirus includes browser Cleanup where you can delete annoying toolbar and plug-ins from your browser.
Download Avast Antivirus.
These toolbar basically get installed along with any other software. And you should make sure that you haven’t selected any unnecessary option while installing a software. There are several other free antivirus programs that you can use to remove malware from your browser. Windows Defender is an inbuilt virus protection program from Windows and it automatically detects unusual activity from any program and alert you about it. Make sure you are updating its definitions regularly.