Problem with vista user connecting to SQL Server 2005

After i had installed SQL Server 2005 on the default instance on vista home edition under local system account. When i tried to connect to the SQL Server database in vista, the login failed. I had spent good 5 hours to dig the problem. I had then downloaded SQL Server 2005 sp2 and installed it. Again when i tried to connect, the connection failed. There is a utility in the location C:\Program Files\Microsoft SQL Server\90\Shared\sqlprov.exe, which needs to be run to provide sysadmin privileges to the vista local user. Before doing this i turned on the UAC for the vista user in the control panel. After giving the vista user sysadmin privileges, i was able to connect to the SQL Server 2005 default instance.