Yes, you can have two OSes installed on your computer. You can have as many as
your hard drive will support. I have five Linux distros installed and Windows
XP. At boot time I get a menu which was installed by Linux. It is called grub.
It allows me to choose what OS to boot into. If I do not alter my selection from
the menu it will boot into Ubuntu, my default OS after 10 seconds.

You downloaded both desktop and server editions of Ubuntu. You need to decide
which one to use. There is no need for the server unless you are running
servers. Have you burned the ISO file to a DVD or CD? That is the first step.

Next, you will have to decide what you want to do with Linux. If you only want
to try it out, you have a couple of options. You can install it from inside
Windows using the Wubi installer. After trying it you can de-install it from
inside Windows.

Wubi will take about ten or 15 minutes to install the first time. You
install the files by putting the CD in the drive while in Windows and then must
re-boot at which time you will see the
Windows boot menu. Ubuntu will be at the bottom. Windows will be the
default OS. I ran Wubi on an older computer with a usb keyboard and I
could not get the bootloader to work until I added a ps/2 keyboard. It
may have been a problem with my old BIOS which does not support usb at
that level. Just bear that mind in case it happens to you. After you select
Ubuntu it will continue to install for about ten minutes or so. When done it
will leave you on the Ubuntu desktop.

You can also choose to run it from the Live CD. You need to have your
BIOS set to boot from CD to do this. You put the burned CD into your
drive and re-boot. There will be a menu that appears. It is grub. It
will give you boot options. For most people, just let it boot through
on its own should do the trick. It will be running from your CD drive and
nothing will affect your computer since the CD is not writable. Anything you do
is for that session only. When you re-boot and remove the CD it will boot into
windows as before. This enables you to see if Ubuntu will work with your
hardware. However, the performance will be slowed because CDs are slower than
RAM. Ubuntu is normally very fast.

There are advantages to both the Live CD and Wubi. Wubi's advantage is that it
allows you try try Linux for an extended period of time. You can make changes
and they will be saved. Each time you boot into Ubuntu it will take up where it
left off. It will also run faster and will give you a better idea of what Ubuntu
runs like in real time. The advantage of the CD is it is portable and it makes
no changes to your computer. It will also get you into Ubuntu faster the first
time since it is already installed on the CD. However, you will have to repeat
the same procedure each time because nothing is changed.

Try it and let us know what you think.