The solution is simple. Install the service for testing, only once. To test newly-compiled changes to the service:
- Stop the service
- Copy new files into the service installation directory, overwriting the old ones
- Start the service
As always, use unit tests, to test code, instead of testing through execution. There is little excuse to not test code, these days. To expedite testing and TDD, I suggest installing NCrunch for Visual Studio (http://www.ncrunch.net/).