install xen-desktop with AD Domain user with windows system user

Question

While login to windows with local administrator and install xendesktop with AD administrator account, it's successful, below is what i have done:

$adPassword= convertto-securestring "password" -asplaintext -force
$adCredObject = new-object -typename System.Management.Automation.PSCredential -argumentlist "ad.mydomain.com\user",$adPassword
$CurrentProcess = Start-Process -FilePath ".\xendesktop\x64\XenDesktop Setup\XenDesktopServerSetup.exe" -Credential $adCredObject -Wait -PassThru -ArgumentList "/COMPONENTS CONTROLLER,DESKTOPSTUDIO,DESKTOPDIRECTOR,LICENSESERVER,STOREFRONT /NOREBOOT /CONFIGURE_FIREWALL"

But while use puppet automation script(it run with windows system user) to execute install xendesktop with AD administrator account, it's failed, below is what i have done to run 'exec' in puppet(same code as above):

$adPassword= convertto-securestring "password" -asplaintext -force
$adCredObject = new-object -typename System.Management.Automation.PSCredential -argumentlist "ad.mydomain.com\user",$adPassword
$CurrentProcess = Start-Process -FilePath ".\xendesktop\x64\XenDesktop Setup\XenDesktopServerSetup.exe" -Credential $adCredObject -Wait -PassThru -ArgumentList "/COMPONENTS CONTROLLER,DESKTOPSTUDIO,DESKTOPDIRECTOR,LICENSESERVER,STOREFRONT /NOREBOOT /CONFIGURE_FIREWALL"

So the only difference is the succeed one run the above script with local administerator and failed one run with windows system user.The failure message display in the event log is like():

An account failed to log on.

Subject:
    Security ID:        SYSTEM
    Account Name:       MyMachineName
    Account Domain:     MyDomainName
    Logon ID:       0x3e7

Logon Type:         3

Account For Which Logon Failed:
    Security ID:        NULL SID
    Account Name:       Administrator
    Account Domain:     MyMachineName

Failure Information:
    Failure Reason:     Unknown user name or bad password.
    Status:         0xc000006d
    Sub Status:     0xc000006a

Process Information:
    Caller Process ID:  0xd90
    Caller Process Name:    C:\Program Files (x86)\Puppet Labs\Puppet\sys\ruby\bin\ruby.exe

Network Information:
    Workstation Name:   MyMachineName
    Source Network Address: -
    Source Port:        -

Detailed Authentication Information:
    Logon Process:      Advapi  
    Authentication Package: Negotiate
    Transited Services: -
    Package Name (NTLM only):   -
    Key Length:     0

This event is generated when a logon request fails. It is generated on the computer where access was attempted.

The Subject fields indicate the account on the local system which requested the logon. This is most commonly a service such as the Server service, or a local process such as Winlogon.exe or Services.exe.

The Logon Type field indicates the kind of logon that was requested. The most common types are 2 (interactive) and 3 (network).

The Process Information fields indicate which account and process on the system requested the logon.

The Network Information fields indicate where a remote logon request originated. Workstation name is not always available and may be left blank in some cases.

The authentication information fields provide detailed information about this specific logon request.
    - Transited services indicate which intermediate services have participated in this logon request.
    - Package name indicates which sub-protocol was used among the NTLM protocols.
    - Key length indicates the length of the generated session key. This will be 0 if no session key was requested.

I have tried to use runasspc also to execute this installation, but I got same result. Any help would be appreciated.