Ok, yes you could edit the files manually.
But, if you're trying to set up for a scripted install for all your machines, you don't want to do that.
You want the information to be in the xml file called from the install command.
"C:\ptc\Staging_Folder\Creo 2.0-m090\Creo 2.0-m090 software\setup.exe" -xml "C:\ptc\Staging_Folder\Creo 2.0-m090\new_install\pma.p.xml"
Personally I don't want to futz around inside these files to change things. I rather do it right to begin with.