A lot of times the ISO images are only 60 or so meg and you would like to put several of them on one cd or dvd. The trouble is, if you burn an ISO image to CD you use the whole disk for one image.
What you want to do is burn the ******.iso files to a cd as data. Then you want to use some software like Nero to mount the image.
When you mount the image it will auto run (mounting an image turns it into a virtual hard drive).
If you use emule, you will notice that some images are over 640 meg and you can't burn them to a cd. What you do in that case, is mount them as a drive and then extract the ISO image you want off of that image.
Now you know what a 5 in 1 image is
