Hi my name is ***** ***** I will be the expert working with you today to help and resolve the problem you have posted.
Windows defender is a default built in security software which comes with Windows 10.
Type windows defender in the cortana search you will see the icon then you can set it as per your choice.
Still if you want to install Trend Micro you will have to go into the installed app and data and remove it from there once removed reboot the computer and then you may download and install a fresh copy your old license key can be reused.
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