How to Remove a Trojan (server.exe) when status is "No Permission to Access"

I bought NAV 5 for Mac today and ran a full system scan. It identified a Backdoor Trojan called server.exe. When I tried to repair it it simply said “no permission to access". How can I remove this file from my Mac? Has the antivirus software effectively neutralised it or not?

I put the file into the trash and tried to use the secure empty trash facility, but it will not delete this file.

Any assistance greatly appreciated.

Regards,

Adrian