>Do an ADIR() to get a list of files in each folder. If any of them have an underscore, replace it (untested, off the top of my head, needs adjusting on how to do the renames I'm sure):

In the off chance you're using an older version of VFP where there is the 65000 element limit for arrays, then you'll need to use the SYS(2000) function (basically used like you're using FindFirstFile() and FindNextFile() API calls). I do remember running into that problem back in the DOS days (i.e. "no one will ever have that many files in a directory" assumption could easily broken). Also discovered when code pages are involved -- in particular anything that uses double-byte character set (such as East Asian languages like Chinese, Korean and Japanese), additional assumptions about the filename could also get broken quite quickly too, especially when you've not set the codepage properly.