how did it get on my PC without me knowing it? I will assume that its not malicious
No, of course not. It was installed for your convenience by the magical software fairy.
Of course it's malicious! To assume otherwise is extremely unwise, to say the least.
This laptop never leaves my house and has never had any viruses
Yes, it never
had any viruses... before. Now it has. How are you so sure your laptop has never had any viruses? A good virus is designed to avoid being noticed. I bet you've never seen a
good toupée, either.
Please run a virus scan on your PC before you do anything else. The results may surprise you.