Here is a list from MSDN:

Which brings up a point I meant to add when I said it depends on the operating system - it also depends on which file system in use.  I believe that FAT has some reserved characters that NTFS does not.

The < > : " /\ | ? *  characters are the ones I usually think of as the illegal characters.  But, 0 through 31 should be added to that.  Using ooRexx, you are not going to get access to Unicode file names.

Mark Miesfeld