Killing a session on windows

I have a database I want to drop on a windows server. Unfortunately I
cannot restart postgres because it is running several live database.

To kill the offending session, I tried select * from pg_stat_activity to
find the PID of the session, and then tried to kill it with command line:

taskkill /f /pid 1234

This appeared to kill the session, but postgres still thinks the session
is live with the same process id.

Using the SysInternals process explorer - there doesn't appear to be a
process with the given ID.

How can I get postgres to drop this session?

Thanks

Howard Cole
www.selestial.com