PostgreSQL: The database cluster initialization failed

I had the same issue installing 9.1.4 on Windows 7. I managed to find a solution online that worked.
The steps I followed are:

1. Uninstall PostgreSQL
2. Delete the postgres user if it still exists.
   

   net user postgres /delete

3. Create the postgres user with a password you can remember
4. Add the postgres user to the Administrators group
5. Add the postgres user to the Power Users group
6. Run a command window as the postgres user
   

   runas /user:postgres cmd.exe

7. Run the install file from within the command window.
   

   C:\Download\postgresql-9.1.4-1-windows.exe

   This should run the installation successfully.
8. Remove the postgres user from the Administrators group.