I know that this is an old thread, but I recently had this issue and found my solution. If you are having this issue,
make sure monitor is in the "PC MODE" and not the "VIDEO MODE". I have a Hannspree 25" and this was the issue.
thank you for the tip, i had a similar problem and it wasn't until i read your post that i thought of looking at my samsung tv.
for the samsung, you have to go under
Menu - Picture - Picture Options - Size
then select "Screen Fit"