problem with istart123.com

[cajo]

I just downloaded Malwarebytes. My first scan detected and supposedly quarantined istart123. When my computer restarted and I clicked Internet Explorer, istart123 still comes up. I repeated the scan and  had 0 detections. I went to history, which showed istart123 quarantined. I clicked delete all items quarantined. I again restarted my computer with the same result. istart123 comes up instead of Internet Explorer. When I googled istart123 it is described as a browser hacker. How do I get rid of it?

[Firefox]

Hello and Welcome to Malwarebytes

Being that you are probably infected, feel free to follow the instructions below to receive free, one-on-one expert assistance in checking your system and clearing out any infections and correcting any damage done by the malware.

Please see the following pinned topic which has information on how to get help with this: Available Assistance for Possibly Infected Computers

Thank you