That's strange that your install packages work since you have OemPreinstall=No. normally that prevents your OEM files from being copied over. How exactly are you installing your 3rd party apps? What method are you using. I suppose your problem could be related to the fact that you are using OEM disks since other people have had problems with them. I can't be specific since the promlems may vary from oem to oem. Make sure that Winnt.sif isn't actually named winnt.sif.txt. It's a common problem. Let the mouse hover over the file. If the tooltip identifies it as a SIF file, then it is okay. If it Id's it as a text file, then it needs to be renamed to Winnt.sif.