Make a sprite from image and put it where your circle is. I don't know the commands for DBC to do this ... sorry I only use DBP.
In DBP it would be: Before your main loop:
rem load image named crosshair.bmp as image 1
rem with no modifications to image
load image "crosshair.bmp", 1, 1
rem make sprite from image 1
rem sprite number, xpos, ypos, image number
sprite 1, xpos#, ypos#, 1
rem set sprite to be slightly see through
set sprite alpha 1, 120
And put this once in your loop
rem move sprite around
rem PASTE SPRITE Sprite Number, XPos, YPos
paste sprite 1, xpos#, ypos#
Hope this helps I'm sure you can do something like this in DBC or you could just make a plain, texture it your crosshair texture, set transparency on, and use alpha channels in your texture to make it partially see through.