diff --git a/.gitignore b/.gitignore
index 818798c..099a840 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@
 *.iso
 *.iso.orig
 *.txt.orig
+*.iso*.extract
 *.img
 *.img.orig
 *.img.enc
diff --git a/Makefile b/Makefile
index 23210e2..e35bbe3 100644
--- a/Makefile
+++ b/Makefile
@@ -43,6 +43,7 @@ clean:
             *.img.enc.orig *.img.orig *.bat \
             *.img \
             *.txt.orig
+	rm -rf *.iso.extract *.iso.orig.extract
 
 # Also remove the large iso images downloaded from remote servers.
 really_clean: clean
@@ -99,6 +100,7 @@ list_images:
 # All the bios update iso images I have checked have had a fat16 filesystem
 # embedded in a dos mbr image as the el-torito ISO payload.  They also all
 # had the same offset to this fat filesystem, so hardcode that offset here.
+# The offset value is bytes in decimal.
 FAT_OFFSET := 71680
 
 # Some versions of mtools need this flag set to allow them to work with the
@@ -273,6 +275,12 @@ $(DEPSDIR)/slice.insert.deps: Makefile
 %.dosflash.exe.orig: %.iso.orig
 	mcopy -m -i $^@@$(FAT_OFFSET) ::FLASH/DOSFLASH.EXE $@
 
+# Extract the "embedded" fat file system from a given iso.
+%.iso.extract: %.iso
+	mcopy -s -i $^@@$(FAT_OFFSET) :: $@
+%.iso.orig.extract: %.iso.orig
+	mcopy -s -i $^@@$(FAT_OFFSET) :: $@
+
 ## Use the system provided geteltorito script, if there is one
 #GETELTORITO := $(shell if type geteltorito >/dev/null; then echo geteltorito; else echo ./geteltorito; fi)
 
diff --git a/docs/HACKING.txt b/docs/HACKING.txt
index 4ca969f..e5b2f79 100644
--- a/docs/HACKING.txt
+++ b/docs/HACKING.txt
@@ -21,8 +21,8 @@ Then start radare with one of these projects:
 
     radare -p x230.G2HT35WW
 
-Makefile targets:
------------------
+Makefile targets for patching:
+------------------------------
 
 If you expect to do development work, the following make targets are
 probably useful:
@@ -65,6 +65,42 @@ probably useful:
 
         make patched.x230.img.test
 
+Extracting the ISO images:
+--------------------------
+
+While examining a new ISO image, it is often useful to extract its
+entire contents.  Due to the way these images are constructed, it is
+not straight forward to get the data out.
+
+The Lenovo ISO image is a iso9660 filesystem image with /no/ files
+in it!  There is a El-Torrito standard boot descriptor in this image,
+and it defines a hard drive image for booting.  This hard drive image
+is a DOS MBR partitioned disk, with one partition.  The partition is a
+FAT16 filesystem, containing the actual files used in the BIOS update.
+
+To access the FAT16 filesystem, the byte offset of the filesystem
+is calculated (via a process of unwrapping and decoding each layers
+described above).  So far, every ISO image file from Lenovo that has been
+checked has used the same offset, so this has been hardcoded in the
+Makefile as the "FAT_OFFSET" variable.
+
+To extract the files for examination, a make target is available which
+can be used on any *.iso.orig or *.iso file.  e.g:
+
+    make g2uj25us.iso.orig.extract
+    make patched.x230.iso.extract
+
+In the case where a file needs to be modified inside the image, it is
+highly recommended to use the mtools "mcopy" utility to copy files back
+into the image - this is the safest method and does not require any
+elevated priviledges or run the risks of mounting foreign filesystems.
+
+If you find you do need to directly mount the filesystem, the following
+command can be used as a starting point:
+
+    sudo mount -o loop,offset=$FAT_OFFSET $ISOFILE $MNTPNT
+
+
 References:
 -----------
     http://forum.thinkpads.com/viewtopic.php?f=69&t=120776