Try selecting the "Rectangular Marquee Tool" **1**

 

Then select "Fixed Size" from the drop menu. 2

 

Then type  1024 in "Width" 3

 

Then type 768 in "Height" 4

 

Then drag the selection to where you want it. 5

 

Once you have what you want..Select  Image > Crop. (Not Shown in image)

 

That outta do it.

 

Hope this helps.

 

Tom

“The fact that no one understands you…Doesn’t make you an artist.”