First off a caution on the Vista dual boot. Don't expect it to stick. Vista has
a habit of trashing Linux when it updates.

As for the desktop dual boot problems, when you install Linux it makes a
difference where grub is installed to. If it is on the MBR of the first device
and you don't change things it usually works without a problem. However, if you
change things through BIOS or by pressing a key to boot a specific device then
you will be in for a surprise, no grub or a grub that won't work. No grub is a
bigger problem. A broken grub is easy to fix.

When you install Ubuntu it does not give you a choice where to install grub and
if you just press Enter it will install it to sda or the MBR of the first drive.
In order to choose where to install grub you need to click on the Advanced
button on the lower right of the final screen where it reviews all of the
changes, just before the installation begins.

If you have a key to press to bring up a boot menu as many BIOSes allow and wish
to boot that way, you should install grub to the MBR of the drive where Ubuntu
is installed. If you don't have this option and don't change your setup, then
you can install grub to the MBR of your main drive (the one that boots by
default).

The first thing to do is to check if grub Ubuntu is installed. You can do this
from the Live CD. The second thing to do is to re-write grub. You can do this
while in the Live CD.

https://help.ubuntu.com/community/RecoveringUbuntuAfterInstallingWindows

Things to know:
Grub uses a different way of naming drives which is relative to where grub is
installed and uses ordinal numbers (counting from zero). If it is to be written
to the same drive where Ubuntu is it will name the drive differently than if it
is on another drive. The drive where grub is written to is (hd0,0) and the other
one will be (hd1,0). If grub is written to a drive other than where your
installation of Ubuntu is the drive numbers will be reversed. The first number
is the drive number starting at zero and the second number is the partition
number starting at zero. Your setup and how you plan on booting will determine
whether grub works successfully or not.

To confuse things Ubuntu uses a different system such as sda or hda for the
first drive and sdb or hdb for the second drive (or sda and hda). This is
determined by their boot order as determined by BIOS and the type of drive (SATA
or IDE).

I hope that this isn't too confusing. Just try to be logical and follow the
guide.