Hello,
http://archives.postgresql.org/pgsql-bugs/2007-01/msg00160.php
I have met the same bug, and resolved it as follows:
1. Open gpedit.msc
Computer configuration - Windows settings- Security settings-Local
settings- User rights assignment
2. Remove all dead SIDs
3. Rename old folder left from previous installation
4. Install again
Thanks
John S. Gakhokidze