Never mind. Been a long day what with spending about 6 hours either in a plane or airport. Turns out the monitor is scaling properly, it's the wallpaper that's not.
I'm stupid, and the above post can be ignored and/or deleted now.
Having some aspect ratio problems I can't seem to find a quick answer for on my own, so will ask here.
Just got a new Dell Studio XPS 8000, and it came with a Dell SP2309W monitor with a 2048x1152 native resolution. Other monitor is a Dell 2709W with a 1920x1200 native res. Video card is a GeForce GTS 240, and I installed the latest nVidia drivers as well as the color profile "driver" from Dell for this monitor.
Problem is, is that I get black bars along both the left and right side of the screen, like you would get when you have different aspect ratios.
On my old system which had a Radeon HD 2600XT, I had this same 2709W monitor hooked up in conjunction with an older 2007FP (1600x1200 non-widescreen) monitor and it worked great.
I've already tried playing with the settings on the monitor, as well as the scaling options in the nVidia control panel. Neither has had any effect. I can zoom the SP2309W in by about 30%, and it fills things horizontally, but then I end up with the vertical ends going off the screen.
What I want to be able to do, is run both monitors at their native resolutions, without having these annoying black bars. So what other things might I try?