Problem solved, Thanks everybody!
for FAT, the string would be 'FAT',0
i don't find any reference that says it may be 1
Thanks!
plutocat,
Please don't delete the original question when you've got a solution, now this post doesn't help anyone else. Thanks.
he had some example code that called GetVolumeInformation
the code tested for the value 1 in the first byte of the lpFileSystemNameBuffer result string
the function normally returns a string like "NTFS" or "FAT"