There is another way you can try, do you use
www.photobucket.com (or)
www.imageshack.us? . Both of these are free to use/join. Upload your photos to them and when you want to include one in your message click on the "yellow" coloured postcard in the 2nd row above the message box.
You will have to cut and paste them from Photobucket or Imageshack but both of these will work for you. (Just remember not to move,resize or delete them from P/bucket or Imageshack after you have posted them or they will disappear from your message).
I am pretty hopeless with computers, I'm almost a complete novice but I have been using these and have found them more or less idiot-proof!