We have tried to stop SpectroSERVER from Control Panel but the service is not responding..

Killing the process will corrupt the DB, but the stop process has been running for 4 hours already.

Please provide some instructions about how to proceed ...

Hung thread

Component : Spectrum Core / SpectroSERVER

When the SpectroSERVER is taking a very long time shutting down, the only options are:

1.  Let it run - which may or may not complete the task in a timely manner (for instance, if it's doing a modeling session from a discovery it may take hours to stop). 
One caveat to letting it try to stop is that the OneClick gui is not available. 

2.  Kill the SpectroSERVER process - then initialize to legacy and reload a previously saved SSdb