Disinstallazione di Java 6 e reinstallazione di Java 7 utilizzando Powershell

Sto usando il seguente script Powershell. La prima metà (disinstallazione) funziona perfettamente. La seconda metà (installazione) funziona solo se consento l'input dell'utente. Qualcuno può fornire assistenza? Ecco lo script: (mi dispiace per la scarsa formattazione)

#uninstall
$java = Get-WmiObject -Class win32_product | where { $_.Name -like "*Java*"}
$msiexec = "C:\Windows\system32\msiexec.exe";
$msiexecargs = '/x "$($app.IdentifyingNumber)" /qn /norestart'

if ($java -ne $null)
{
    foreach ($app in $java)
    {
        write-host $app.LocalPackage
        write-host $app.IdentifyingNumber
        C:\Windows\system32\cmd.exe /c "C:\Windows\system32\msiexec.exe /x $($app.IdentifyingNumber) /qn"
        Start-Process -FilePath $msiexec -Arg $msiexecargs -Wait -Passthru
        [Diagnostics.Process]::Start($msiexec, $msiexecargs);
    }
}
if ($java -ne $null)
{
    foreach ($app in $java)

{
        write-host $app.LocalPackage
        write-host $app.IdentifyingNumber

C:\Windows\system32\cmd.exe /c 

"C:\Windows\system32\msiexec.exe /x $($app.IdentifyingNumber) /qn"

        Start-Process -FilePath $msiexec -Arg $msiexecargs -Wait -Passthru
        [Diagnostics.Process]::Start($msiexec, $msiexecargs);
    }
}

function Get-ScriptDirectory{
    $Invocation = (Get-Variable MyInvocation -Scope 1).Value

try {
        Split-Path $Invocation.MyCommand.Path -ea 0
    }

catch {
    Write-Warning 'You need to call this function from within a saved script.'
    }
}

function Get-Architecture{
    return $(gwmi win32_operatingsystem).OSArchitecture
}


$Path = Get-ScriptDirectory

#Close all instances of IE, Firefox, & Chrome
Get-Process | where {$_.ProcessName -match "iexplore"} | Stop-Process -Force
Get-Process | where {$_.ProcessName -match "chrome"} | Stop-Process -Force
Get-Process | where {$_.ProcessName -match "firefox"} | Stop-Process -Force

#Install
Start-Process -FilePath "msiexec.exe" -ArgumentList "/i "C:\temp\jre1.7.0_17.msi" ""/log "c:\temp\javainst.log " -Credential $cred -wait

#Also Install the 64-bit JRE if on a 64 workstation

if(Get-Architecture -match "64")
{
    $cred = Get-Credential
    Start-Process -FilePath "msiexec.exe" -ArgumentList "/i "C:\temp\jre1.7.0_17 (x64).msi" ""/log c:\temp\javainst.log " -Credential $cred -wait
}

#Import reg keys to disable auto updating
reg import "C:\temp\JavaUpdate.reg"{ 
    }