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The .sfv file contains the CRC32 checksum that is used to check the file integrity (or download errors in the file) and is not needed to play the file... Usually the checksum is included as a part of the filename, though some groups prefer to use a .sfv file for this information.
You can download this utility that can recreate the CRC32 checksum, which you compare against the .sfv value. Any difference indicates file corruption...
SfvCheck - Free Software Downloads and Software Reviews - Download.com