Windows vista has no problem. Just plug in and use. For Ubuntu, originally I used a small script to change the configuration file /etc/X11/xorg.conf accordingly and restart X to obtain several options. see
http://ubuntuforums.org/showthread.php?t=361124
In fact, by using nvidia-settings I can change the display configuration as easily as in windows. First plug in monitor cable, then being root, type
$nvidia-settings
A configuration GUI will pop up. I can disable/enable any monitor as I want and apply changes immediately without restart X. Good thing, Nvidia!

I have reinstalled vista and ubuntu in my Dell XPS 1330 last
week. Here is a little note for future reference.

Configuration history of myDell XPS1330

shipped with vista preinstalled. Patition as follows
1: Dell Utility. Small partition less than 100Mb
2: Recovery. 10Gb
3: OS. Vista installed
4: Media Direct. 2 Gb
I used vista's own disk management tool to shink the OS drive to about
80Gb and used the left space for ubuntu installation. After ubuntu
installation, grub setting was OK. Dual boot was good.

Wanted to get rid of 10Gb recovery and wanted to seperate the system
partition and data partition for vista.

Reinstall vista and ubuntu

First the installation DVD of vista has serious bug when partitioning
the hard drive. Used Media Direct installation CD to partition the hard
drive. Prepare C: and D: drive besides Dell Utility and Media Direct
drive. C: is 40Gb for vista installation. Then install vista in drive
C: using the installation DVD without changing the partition. Install
vista as instructed.

After vista is installed suscessfully, boot into vista, partition D:
drive into another 2 partitions. One is 80Gb and formatted with NTFS,
the rest 35Gb was used for Ubuntu intallation.

Use Ubuntu live CD to install ubuntu. Use 5Gb for swap from the 35Gb
partition. Use the rest 30Gb for linux installation formatted with
ext3. Mount the windows OS partition and windows data partion to
/windows and /windata. No need to mount the other partitions.

After Ubuntu installation, the grub should be configured correctly and
dual boot should be good. I customized the grub menu by booting into
Ubuntu and editing the grub configuration file
/boot/grub/menu.lst. Move vista to the default system to boot.