What is your program - Photoshop Elements (photo editor), Premiere Elements (video editor) - and what version of the program(s)?
How are you downloading photos from the Canon 20D into some Elements program? What are the properties of these photos - pixel dimensions and how many?
If you are using Photoshop Elements, then you have posted in the wrong forum. Your thread somehow got posted in the Premiere Elements Forum (video editing).
Before going further, let us stop here and get the above information that will help us help you.
The answers will be in the details. Any questions or need clarification on the above, please do not hesitate to ask.