SD2IEC is a modification of the Commodore 64 kernal with improved support for the wonderful SD2IEC device by Ingo Korb. Either burn the 8K kernal file to an EPROM and replace the original kernal ROM chip of your C64, or use a device that can override the kernal ROM (e.g. 1541 Ultimate, Turbo Chameleon 64, EasyFlash³)

One of the best features of this ROM is the built-in file browser amongst other features such as fast loader, dos wedge and function key mapping.  See the readme.txt file in the archive for more information.