There's no difference in using Dart for a Windows service as any other executable; you just need to call dart.exe with the correct arguments.

However, Windows doesn't support running arbitrary exes as Windows Services, as they require a little metadata/bootstrapping. I've had good experiences with NSSM - the Non-Sucking Service Manager. In the comments, SC.exe was suggested; but I was unable to get it running on the latest version of Windows Server :(