People with little to no knowledge on the subject have failed just using IC. Some people with basic knowledge and IC have barely passed. Some people with good knowledge and IC have passed easily.
If you have little knowledge or basic knowledge, you will need to study alternative sources as much as possible.
To gauge your knowledge, see how many of these questions you know without a doubt.
http://www.petersons.com/pdf/clep_informationsystems_q_print.pdf#toolbar=0&zoom =100
If you know that you can answer 50 of these without a doubt you will be ready. If you can answer 25 without a doubt, and pretty sure about an additional 50, then you will be ready. Any less on either, and you need to study more. Please utilize the links as much as possible. If you have the time, my suggestion is to go to a book store for a few hours and read a dummies book on computers.