Norton is one of the first things I uninstall on people's Windows machines when I encounter it in the wild. The zombie corpses of both Norton and McAfee consumer products seem locked in a head to head battle to produce the worst, most ransomiest security theater software they can imagine.

What should I use instead?

I tend to recommend Windows Defender.

Since Windows 8, Windows Defender has an antivirus out of the box in every ordinary Windows install. If you are uninstalling Norton or McAfee you may have to do some extra work to untangle the hacks those programs tend to use to disable Windows Defender.

For Windows 7 (and XP if you are crazy/desperate) the antivirus component of Windows Defender was called Windows Security Essentials and had to be downloaded separately due to the statute of limitations in the EU anti-trust decision. You need to be careful that you find a legitimate Microsoft link for Security Essentials because there were a number of trojan horse authors that took advantage of this being a required separate download.

OK thanks. It's Win 10.

Bitdefender or Kaspersky according to https://www.av-test.org/en/antivirus/home-windows/

To check untrusted files that are not sensitive, you can use https://www.virustotal.com/ which will check them with all the major antivirus software.