Point: I am a newbie.
Point: I am not a TOTAL newbie.
Point: I am now bald from trying to figure this out.

I'm on a standard Emachine D-series with the following specs: 1.5 TB Barracuda hard-drive, 2 gig ram, AMD64 Athlon processor, dual-boot with LILO, Windows XP and Slackware 12.1. My card is an nVidia Geforce 8400. The dual-display works wonderfully on the Windows side, but I need it for the Slackware in order to work. The original setup was just the standard 1024x768 monitor, but I put a 1280x1024 on the non-VGA (can't remember name, white plug with an equal-arm cross as a connector) head. The card defaults to that now, even without changing any settings in Slack.

What i've done so far:
1. su'd up and did 'X -configure'. I tried out the new settings, but nothing ever loaded.

Granted, i could just be impatient, but i'm not sure.

bluedragontao,

did you search the LQ forum? google? There's a search feature on the right hand side. Plenty of references to what you need.

search for dual monitors and twinview

here is a link to a good aggregate of what could help you.

HowTo: Dual Monitors