This code (powershell), creates a predefined computer (with a random mac)
$Cred = Get-Credential
$DSMs = New-WebServiceProxy -Uri "http://172.16.0.3/Altiris/ASDK.DeploymentSolution/DSTaskManagementService.asmx" -Credential $Cred
$ComputerName = "WS01"
$Mac = ('{0:X2}' -f $(Get-Random -Minimum 0 -Maximum 255) + "-" + '{0:X2}' -f $(Get-Random -Minimum 0 -Maximum 255) + "-" + '{0:X2}' -f $(Get-Random -Minimum 0 -Maximum 255) + "-" + '{0:X2}' -f $(Get-Random -Minimum 0 -Maximum 255) + "-" + '{0:X2}' -f $(Get-Random -Minimum 0 -Maximum 255) + "-" + '{0:X2}' -f $(Get-Random -Minimum 0 -Maximum 255))
$InputXML = "<DeploymentItem><ItemType>Resources</ItemType><ItemName>PredefinedComputers</ItemName><ItemAction>add</ItemAction><Item><Computers><Computer>$ComputerName,$Mac,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,</Computer></Computers></Item></DeploymentItem>"
$DSMs.RunDeploymentSolutionTask($InputXML)