[DotNetDevelopment] Windows Service Shell access denied

[depp]

Hi,
I try to run a DOS command from a win services
the command :
DTExec.exe /DTS "\MSDB\FileName" /SERVER IP /CONFIGFILE "Path"

However the command works on cmd but not in the code using
System.Diagnostics.ProcessStartInfo object,
I tried to set account :

System.Diagnostics.ProcessStartInfo procStartInfo =
                new System.Diagnostics.ProcessStartInfo(fileName ,
command);

                GetUser(ConfigFile); // get user Doamin and pass form
XML FILE
                foreach (char c in PassWd)
                spwd.AppendChar(c);
                procStartInfo.Domain = Domain;
                procStartInfo.LoadUserProfile = true;
                procStartInfo.UserName = user;
                procStartInfo.Password =  spwd;
                procStartInfo.RedirectStandardOutput = true;
                procStartInfo.RedirectStandardError = true;
                procStartInfo.UseShellExecute = false;
                procStartInfo.CreateNoWindow = false;
                System.Diagnostics.Process proc = new
                System.Diagnostics.Process();
                proc = Process.Start(procStartInfo);
                …
Error : access denied

the Win Service runing under ServiceAccount.LocalSystem
any idea ??
THX