I founf a trojan with avast but it's on a system file, should I delete it?

Avast should ask you if you want it to repair the file. If it can do that, that is your best-first option. Second choice is to quarantine it and let it sit in the vault for a week or so while you go about your normal activities. This way you will know shortly whether or not the file is critical.

In any case, *don't* delete it until you've made the above determination.

I founf a trojan with avast but it's on a system file, should I delete it?nortin

Quarantine it (put it in the chest). This way, if it damages anything it can be restored. Bear in mind that trojans may either damage system files or put their own files in system folders to look genuine.

I founf a trojan with avast but it's on a system file, should I delete it?pc security

Put it in the Chest, so the removal can be undone if you have problems.

Malware in the Chest can do absolutely no harm.