New installation "The Service Name is Invalid"

I'm trying to install postgres on a windows vista-home-premium system.

I downloaded postgresplus-8.4.1-2-windows.exe from www.postgresql.org.

The installer runs without problem (just asks me to choose a sysadmin password).

When I try to start the server (Green triangular icon), I get the error

"The service name is invalid.
More help is available by typing NET HELPMSG 2185.
The start command returned an error (2)"

I've checked, and there is no service that looks even vaguely postgres related.

I'm using an administrator account to do the installation.

I've tried the usual:
* rebooting
* uninstalling/reinstalling
* disabling anti-virus

Any suggestions?

Thanks,

Greg