>Fullpath() doesn't do any validation on the file name

Thats misleading. If you have SET PATH TO c:\DIR1, c:\DIR2 and SET DEFAULT TO c:\DIR3 doing a Fullpath() will search Dir3, if nothings found, it will search Dir1 and Dir2, so it does try and find a valid file but only in the default dir and VFP Paths. But not the windows path or anyhting.