NOTE: Numbers beginning with 0x are in hexadecimal format.

What's needed:
- a hex editor (I use HxD)
- a Darksiders 1 options file (options.dopt)

Steps:
1) Open options.dopt in your hex editor
2) Change the 01 at offset 0x15 to 00 (see disable_fullscreen.png)
3) Save options.dopt in the hex editor
4) If necessary, move options.dopt back into the Darksiders folder under AppData\Local (Application Data on Windows XP)

Credits:
I figured this out by looking at the options file posted here

This is such a great series.

This is great! Thanks a lot, worked like a charm! =)

Do you know if, maybe, one of these options influence camera speed with a controller's right analog? I know mouse sensitivity doesn't influence.

I would play with M&K, but everything else apart from camera movement is a lot better with the controller, and I started feeling the camera more after I got the "boomerang".

Thanks again! =)