how to resolve The service did not respond to start or control request in a timely fashion, you need administrative privileges to be able to start/stop this service. (sqlsac)

hi when i was installing sql server 2005 express edition on win vista the following error being appeared : The SQL Server service failed to start. For more information, see the SQL Server Books Online topics, "How to: View SQL Server 2005 Setup Log Files" and "Starting SQL Server Manually."
it was working 2 days ago but after some changes that i made in network hardware it crashed.
this is the end part of log file :
<Func Name='LaunchFunction'> Function=Do_sqlFileRename <Func Name='GetCAContext'> <EndFunc Name='GetCAContext' Return='T' GetLastError='203'> Doing Action: Do_sqlFileRename PerfTime Start: Do_sqlFileRename : Wed Apr 20 00:38:26 2011 <Func Name='Do_sqlFileRename'> <EndFunc Name='Do_sqlFileRename' Return='0' GetLastError='0'> PerfTime Stop: Do_sqlFileRename : Wed Apr 20 00:38:27 2011 MSI (s) (3C:B8) [00:38:27:007]: Executing op: Actio ...