This howto is for Microsoft OS'es only.
1.Gather your image and the files you wish to lodge into it. Here I have a meeting.txt which which I will slap inside my secret.jpg
2.Add the files you want to hide into a new RAR archive
Open Command Prompt
3.Go to the folder where your files are located, in this case 'C:\hidden'
Type 'copy /b secret.jpg + meeting.txt.rar lizard.jpg' where secret.jpg is the original picture, meeting.txt.rar is the file to be hidden, and lizard.jpg is the file which contains both.
4.Test the JPG by opening it, and verifying it still opens. If it does, try opening the file with WinRar!
5.The completed RAR file!
The link to the original page:
http://www.thetechtray.net/2007/05/30/hiding-files-in-jpegs