This is a PPWIZARD command line switch.
By default PPWIZARD deletes any generated files when an error occurs. This makes it more friendly in normal MAKE files which will then correctly restart the build process. You may wish to promote warnings to errors using the "Warnings" option.
If not disabled, PPWIZARD will on error delete all files that it knows about, so in some cases it relies on you having correctly indicated output dependancies with the #DependsOn command or AddOutputFileToDependancyList() routine. PPWIZARD will ignore file deletion errors (what can it do?).