updating windows installation

Last month I installed the windows version of 8.0 RC1.  The installation

installed postgresql as a service with user “postgres”, and an associated

password.  “postgres” is a service user, not a standard user.

Yesterday, I uninstalled 8.0 RC1 and then installed 8.0 RC3.  That worked,

once I realized that the “postgres” service user was never deleted, and

that I could only install RC3 if I remembered the password from RC1.  I guess

I could also use a different name for the service user.

It seems that I may be able to change the password for the postgres service

user IF postgres is still registered as a service (before I uninstall).  But, if I have

already uninstalled postgres, can I still change the password of delete the user?