Accessing samples from SD card?
The Spectralis will not recognize SLC or SLI files on the SD card if the file system is not FAT16. But however - you can't access samples directly from the SD card. Instead of that the samples will be copied onto the internal flash memory. But even then - no need to browse files. The Spectralis lists the included samples of the files inside the oscillator wave menu.
Using SD cards makes not really sense in general. USB2 transfers are much faster than transfers from the card to the internal memory.