A few things that everyone should know, especially if you are working with a designer on a project.
-It is always easier to shrink something than enlarge it (you can't make more pixels from nothing)
-Always start with a large image and shrink to fit your desired size (especially if you are going edit it first)
-For *most* print jobs the original image should be 300 dpi
-For logos, you should always have a vector (.eps) file of it if possible
Now, for your presentation, I'm guessing you are working with what you have. The best you can try is to go to
Filter > Sharpen (good luck, it doesn't do that great of a job, and the larger you go from the original size the worse it will be).
Hope that helps, and sorry for the rant, but I get this all the time...