Media Generators size problem

Hi guys,

I'm making one lj movie in Sony Vegas and I face one problem. If you watch this http://img218.imageshack.us/img218/2997/vlcsnap20724tw5.png picture you can see that the media generators which I used cover only chosen part on screen...not whole (sides are not affected). I don't know how to set the size.
Input video has 1280x800 resolution and the final movie will be 800x500 (both 16:10). I tried to set media generators resulion 1280x800 and 800x500 too and the final movie has the same unwanted effect.

Someone knows what I do wrong? Thanks in advance.

Thx Spaniolu but the problem was in Render As option: Stretch video to fill output frame size. I turned it on and now it's OK.

So this problem is solved. :)

bye