ok im not all that familiar with raident but i tryed doing some texturing step by step and my brush does not look anything like the tutors version.

it turns out all black and red, and you see only streeks of red and black running the length of the brush.

what cani do to fix it?

First lets try a few things and tell me how they work. A picture would help a lot.

Highlight your brush.
Press "s" to bring up the surface inspector.
About halfway down, click on "fit".
This will make your texture the size of the face on the brush.
You can undo this by clicking on your texture again in the texture list.

A few things to troubleshot further.

Take a "printscreen" by loading your editor and looking at the trouble spot. Hit the "Prt Scrn" button. Load up MSPaint and "Ctrl v" to copy it into the space. Save it as a .jpg and upload it, I like to use imageshack.us. Post the link.

Is it a custom texture?
Is it a brush or a mesh, if your not sure then its a brush.
Link to tutorial?

your graphics card probably doesnt support Dx9

Or you don't have the Dx9 drivers installed.. you can download those at microsoft.com.

install them.. try again.. if the brushes still turn up red and black, your card does not support DX9.