Which one are you trialing?
Used to use AVG but it got overbloated.
If you bank with Barclays you can download Kaspersky free form your banks web site
Avast is considered as one of the best free ones for stopping viruses and malware, although it now has a impact on system resources and does "nag" you to upgrade. I used it for years now without a problem.
Avira is also considered to be good.
DO not rely on windows defender as it is poor for stopping viruses (viri?)