Internet was down for a while and I needed something to do. This is how to hide stuff in a JPG image. It might work for other images...I haven't tried yet. Only for Windows.
1. First you need a winrar file and an image. The image should be easy. I'll be using 'SHINYDEVICE.jpg'. For the winrar just right click, then choose new, then winrar archive. If you don't have winrar then get it. Its useful. Rarlabs.com
2. Open the command prompt. Everyone should know how to do this, but if you don't then its Start -> Run and then cmd.

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3. Right click the image. Choose 'Properties'.
4. Copy the line thats in the 'location' place thing.
5. Go back to the command prompt. Type in 'cd ' with the space, then right click and choose paste to paste the location. Press enter.
6. Now type in 'copy /b yourimage.jpg + rararchive.rar hiddenfiles.jpg'. Obviously you want to replace Yourimage with the name of your image, rararchive with the name or your rar file, and hiddenfiles with whatever you want to name the thing to hide stuff in.
7. Hopefully you get something like this. If not then you screwed up.
8. Right click the new hidden archive. Click Open with and then Winrar. You might need to click the choose program and get it yourself, but after the first time it will be on the list.
9. I really don't know why I made a picture of this step. I guess its the "Oh look, a RAR' step.
10. Drag files in. They are hiding now.
The end.