Most common drivers are supplied with the live CD (the download). You
will need to burn a DVD or make a thumb drive with the ISO image you
download. You will find instructions to do this on the Ubuntu website.
It is best to connect the computer to a wired lan as not all wifi
adapters drivers are on the disk. This can be tested easily though by
starting up with the try Ubuntu option. You will likely see a blurb in
the top right letting you know a connection is available, if one is the
wifi is seen by Ubuntu.

I would not bother with a reinstall of windows that would be the first
thing you would do for a dual boot system (ability to start up in more
than one OS). The reason is the lack of drivers that I would not. You
could reinstall Vista because you likely have the drivers for your
machine. You would want a working windows system before installing
Ubuntu if dual boot was desired.

With only few exceptions selecting install Ubuntu, and then install
Ubuntu alongside, are all you need to know to install Ubuntu as a dual
boot system. I suggest installing Ubuntu while connected to the net.
Select both install third party software and update while installing. As
a beginner you will be happier with the choice if you do so.

I also suggest you open Ubuntu software center that is on the launcher
to the left, just mouse over each Icon and it will tell you what it is.

I suggest installing "Synaptics package manager" right off the start. I
also suggest you browse the software center at this time. Using the
search window you can find applications you have use of. You don't need
a program name just what it does.

If you need a disk utility type in "disk". You do not need to ask if
anyone else has used the program you want to try, just try it. You see
most Applications are free of charge. You will no longer need to go to
the store to buy a program. You will no longer need to go to
questionable sites to download freeware type programs that may include
viruses. You will just install using Ubuntu software center or Synaptics
package manager.