To regrind multiple directories I use a batch file that deletes GNDDBF30.XXX from the dated subdirectory, wait a few seconds and grind should run one day after another. I would not delete this file for more than 10 days at a time, so as not to discombobulate grind.exe. and if it hangs up just find the dated subdirectory that it is grinding and copy GNDDBF30.XXX from another directory.