Partitions are logical divisions of your hard drive.  Think of the hard drive being a pizza.  When you make a pizza you can cut the one pizza into multiple slices.  In that sense, a partition is a slice of your hard drive.

Most people who run Windows have 1 partition, the one labeled C:\.  Some people who run windows have a second partition called the recovery partition.  It is installed by the computer's manufacturer to be used to wipe/reload windows.

To install Ubuntu, you need 1 of the following:

1) Unnalocated space on the hard drive.  Unnalocated space is the part of the hard drive that has not been made into a partition and therefore is empty (it is more complicated than that, but for practical purposes, lets say it is empty).  Ubuntu would then "format" the unnalocated space to turn it into a partition Ubuntu can use to install it's operating system.

2) A partition that does not have anything you want to keep on it.  Ubuntu can empty the partition and then install it's own operating system on it.  Doing this destroys all data on the partition, so if this is your Windows partition, you cannot use Windows anymore (unless you re-install Windows).

A lot of people, when installing Ubuntu, do what is called dual boot.  Essentially the hard drive is split into two partitions, one for Windows and one for Ubuntu.  The user can then select which one they want to boot to when they start the computer.  Doing this is relatively simple.

step 1: Install Windows on the computer.  When it gets to the part of the installation process, create a partition for Windows that is at least 20GB but leave enough unnalocated space for Ubuntu.

step 2: Install Ubuntu using the space not used to install Windows.

It is important to install Ubuntu second.  The reason behind this is the program called the boot-loader.  This program is the first thing called by your motherboard to boot your operating system.  When you install Windows, it installs microsoft's bootloader that boots Windows operating systems.  When you install Ubuntu, you install Ubuntu's boot-loader that will boot Ubuntu and Windows.  If you install Windows again after that, Windows will install Microsoft's bootloader, causing you to only be able to boot into Windows.  At this point, you either start the process over again or manuall install GRUB and configure it.

All right, so if my computer has a single partition (which it does), I would need to first split the hard drive into two partitions, reinstall Windows on one, and then Ubuntu on the other?

Lols, I was bought a machine with those exact same specs for xmas last year. It came pre installed with Vista. That machine cannot run vista. First thing I did with the compy was check how much of the ram was being used - 450/512mb. That's with a clean install. I uninstalled all the crap that Acer foisted on to me and it dropped to about 256/512 in use. That wasn't enough for me so I tried to install XP. Used the Windows formatting tool and put in the xp cd, it didn't install and I had to restore Vista. I then got xubuntu and an open source formatting tool, it managed to find the hidden partition (partition 7 apparently) that was giving my computer instructions to not install xp and formatted it. I then dual booted xp for gaming and Xubuntu for everything else.

My point is, I also rate linux highly, and 512 mb of ram is much more than XP requires

 No; ignore Senlis - he's making it uneccessarily complicated. The Ubuntu disc will DO IT FOR YOU if you only have one Windows partition at the moment. Select "shrink main partition and use freed space" and it will create the partition without damaging Windows.

My point exactly!

Seems like there's a lot of love for Ubuntu lately, I never did like it myself, got tired of dealing with sudo. I always preferred Gentoo back when Emerge was boss and other distro's didn't have anything to compare.

Since i haven't used Ubuntu in awhile, do you still have to use sudo for everything? Or have they cleaned that up a little?

which distribution do you have?

You both are making this unnecessarily simple. He should dd the first 512 bytes of hda to a temp file, make the necessary changes to the partition table in ed and dd it back :P

back in grad school i used ubuntu a lot, mostly for research, which is good since a lot of academic stuff is available only for linux. but the whole issues with dependencies and what-nots is an utter pain in my rears...

ubuntu didn't really offer anything i couldn't do in windows, and eventually i switched back to windows and just started using cygwin and x-win32, which isn't free.

by now, i've grown out of my "must use something other than Windows" phase and i think i'll be sticking to windows for a while.

I remember when Red Hat used to offer the ability to do a "local" partition within your Fat or NTFS partition, it ended up making your windows run maybe 25-30% slower then normal, it was wacky.