This is where you'll learn that a dual boot is a must, in all honesty Linux does not have an extensive list of user friendly tools or applications, don't get me wrong all of the tools you'll find for any job are in the Synaptic Package Manager(don't forget to read up on repository's and how to enable them) most of the open source applications take a little command line knowledge to get working at the worst of times and for video editing there are not a whole lot of options whereas in Windows there are countless.
Use Firestarter to manage your firewall(or if your bored look into iptables)
Remember any tools you use has a help file alongside it, to use it for firestarter open a terminal and type man firestarter.
All in all Linux is best as server, so if you wnat to host a media server for you other machines on your network XBMC(X-box media center) is a good choice.
To find any software search through Synaptic Package Manager and it usually turns up a lot of interesting results.
As I said Windows is best at some things and Linux is best at others, if you come to not like it as an everyday OS you'll learn the power of it's networking capabilities and keep Ubuntu as one big tool
Both of which have improved massively the last year or so. Heck, even r600/r700 have basic 2D acceleration and XV up and running in radeonhd from git. Things are moving along, just not very fast. With only a handful of developers that's all you can reasonably expect to be honest.
Wouldn't say it's that bad. My first step into the *nix world was FreeBSD and it now runs on all my servers. The ports tree under FBSD makes life quite easy for "n00bs" too I think.
Back when it was my one and only desktop box too, I ran WindowMaker under X for a GUI
Considering that your level of expertise is fairly low, I'd recommend Ubuntu, as you're already familiar with it.
To be completely frank, Ubuntu, Fedora, and OpenSUSE are all quite easy to use. But different people have different level of success in using them. For example, I find Ubuntu and Fedora works well on my system, but OpenSUSE does not. Other people differ.
I started using Ubuntu, and then got involved in testing alpha and beta releases to learn to solve problems. After I got familiar enough, I started playing around with Fedora, Debian, etc. I've now settled into the Debian testing release (Lenny).
Ubuntu is built upon Debian (the unstable branch of Debian, Debian Sid). So once you feel you want to learn more, you can start playing with Debian, and then try out some harder distros like Arch, Gentoo, or Slackware.
Hmm I wouldn't go that route.. I've tried it a couple of times and it's always been problematic for me. I'd go the clean install route, especially as Linux is so damn quick to install compared to Windows.
If you're really used to Windows layout etc. I would suggest Kubuntu, it's the same as ubuntu but with a KDE desktop which is very similar to Windows, (but obviously different too).
Xubuntu, Ubuntu, Kubuntu are all exactly the same operating system, the only difference between them being the choice of desktop and applications loaded with the distro, (a lot of which are tied to the desktop chosen).
When you originally tried the installation are you sure it wasn't telling you that it was going to install the root to 100% of the partition? I seem to recall a warning along those lines if you don't create swap and et3 partitions too. Installing Linux on to just a root partition isn't the recommended way, hence the warning IIRC.
As John says, you really need to have a basic understanding of partitions, (which you obviously do as you've managed to partition your windows drive), then upon install of Linux you will need to allocate space from your unallocated partition space to / "root" /swap and /ext3 for the rest. There is a drop down list where you can choose the partition types in the install wizard under manual.
I've always chosen 2-4GB for the root partition and made the swap partiton the 1.5x to 2x my physical memory and filled the remaining with the file system.
Why not stick with Windows then? It's a different OS ffs, they're not supposed to be similar. It's completely against the philosophy of the whole project.