How To Non-Destructively change an external HD Filetype On Mac (Without Loosing Data)

I don't believe you can do this without losing data (is 'loosing' data the opposite of 'tightening' data?). The 'filetype' is an inherent structure and method of laying down data on the drive. Changing it, by nature, requires a reformatting of the whole drive I believe. you can't mix and match...maybe in partitioning, but even then to partition, you need to start from scrath I believe.

Can you transfer the stored info on it to another drive in the interrim, re-format, then pull it all back?

 

you cant change it on the fly, i dont know any method anyways but you might try using a program for zipping files like .rar for example betterzip you can split them that way.

and when you want to use them you take them back to a filesystem that supports more then 4gb and just unzip it

 

Unfortunately youll need to put them on another drive, reformat your buffalo drive to the mac format then drag them back on. When an OS has to change the format of a drive that drive will lose all info.