What you probably want, can easily be accomplished using the Task Scheduler API
You can use something like this A New Task Scheduler Class Library for .NET
] to develop your solution in c# or just import the COM interfaces yourself.
The really easy solution is to use the tools included with windows
Another benefit is that your solution no longer needs to be implemented as a service :) - it will be executed under the scheduler service, and will run even if there is no currently logged on user.