You have already run a virus check, but you may think about running another one to scan your system. Possibly something like Malwarebytes.
You can use msconfig.exe to check the startup items and uncheck that entry if you find it. If you cannot find it, you might download a program from
SysInternals called
Autoruns which will see everything that is starting up. Run it as admin to get the best results.
Have you searched the registry for a
\server.exe entry. If you find the correct on, it might help pinning down where the problem is originating.