Have you looked in the errorlog file the source of the problem. The file is located sybase\ASE-12_5\install. In this directory you should see the other batch files that you could launch to determine if the problem is W2K3 or a setup error with Sybase.
Since Windows 2003 modified the interface of service calling, ASE ( lower than 12.5) could not start from Service any more.
For ASE 12.5, you should apply the latest EBF. Then you can start it from Service.
For ASE below 12.5, you can start ASE in CLI(Command Line Interface).