Included in this torrent are four files:
        README - This document
        cd51.iso - A 7MB bare-bones installer that requires a network connection
        install51.iso - A 236MB full installer.
        SHA256 - SHA256 checksums for the above

The iso files are meant for 64-bit PC architectures.  They won't work on anything else.

All files were originally downloaded from http://mirror.ece.vt.edu/pub/OpenBSD/5.1/amd64/
OpenBSD's install guide is at: http://www.openbsd.org/faq/faq4.html