PostgreSQL won't start

Last week I set up Postgres 8.3 on a WindowsXP machine.  Had it up and
running and imported data.  Now when I try to start the server (after
a machine restart) I get the message:

********************************************************************************************
pg_ctl: another server might be running; trying to start server anyway
PANIC:  could not open control file "global/pg_control": Permission denied

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
server starting
********************************************************************************************

In the archives I've seen suggestions to make sure to start using the
postgres account (I am), make sure postgres is configured as a service
(it is), and make sure global/pg_control and the rest of the
PostgreSQL directory has read/write access (it does).  What else can I
try to start the server?

Thanks,
Lee Hachadoorian
PhD Student, Geography
Program in Earth & Environmental Sciences
CUNY Graduate Center