I'm only new to Tableau, and I'm currently only using the Reader product. I've downloaded the latest version to my Laptop (using Windows 7). But the Dashboards I'm looking at are all crammed up to the top left of the screen, and a lot of the names are cropped. So on my screen I'm taking up about two thirds. I've change all resolutions and such but to no improvements. So I've got all this grey space to the right and below
If the dashboard has been defined as a fixed size then that's how it will work. If the dashboard is created with "automatic" sizing then it will take up the space you're talking about.
Almost every dashboard I create is a fixed size, so you would always see the white space around the outside of the dashboard.