Flash embed screen resolution issue

I have created a Flash file that is 640 (width) x 480 (height). I inserted screenshots containing text into the movie. When I view the exported swf file in a flash viewer at the exact dimensions (640×480)it looks great, the text in the images is perfectly clear. However when I embed the file into my blog (using Kimili Flash Embed) it looks terrible, I guess because of the different screen resolution (also if I make the window of the flash player bigger it makes the text look bad). Is there anything that I can do to ensure that the movie is always shown at 640×480, no matter what the screen resolution is?