You can use a boot CD, like Hiren's Boot CD or make your favorite USB key as a boot.
Google search gave me :
I used a USB key (With Win95 or 98 DOS) and copy all my favorite DOS tools on it, it is faster than a CD-ROM. With XPS after DELL logo when you hit F12 on boot you can choose HDD, CD or USB.
Ok the Hp thing worked for me. I can't believe there's no other way to make a a bootable USB DOS other than Windows...
Now I have another problem, when I try to start the plist editor it give me an error dialog box: codec overrun.
Sorry to 'overrun' you with my many problems
EDIT: bah, I went to get it myself on google. but just so you know, your zipped file has probably a bad checksum.
So what I need to modify in plistedit?
I guessed that you have to edit the plist inside the nvinject.kext, but I'm a bit lost in it. I see several references of NVCAP.
The one that seems relevant to me is root>IOKitPersonalities>NVinject>entriesToAdd>NVCAP (data)
Is that right?
Even if it right, I can't make it work. You press FN+F8 to activate the dual screen right? because when I do so, the Hackintosh freeze, I have to press the power button for 4 sec to reboot. And I have the same NVCAP as you.
Any ideas what goes wrong?