Alternative to a Windows Service

I am using a Windows Service on a Windows 7 PC but it is not working too well because of security issues. I want to know what could I use instead of a Widows Service? The service at the moment runs inside a Windows Application and calls a Web service from there and has a few classes of it's own.
I need either a Windows application or a WCF Service to do what the Service does. Or maybe someone can suggest something better?