Let's say you decide you like Ubuntu, or at least you want to give it more of a try, in that case you can choose to install it on your hard drive. This does not mean you have to blow away your Windows partition. Far from it! Just let Ubuntu set up a part of your hard disk for itself and you should be fine.
Tip: In theory, you need only 2GBs of disk space for Ubuntu. Don't believe it. Set aside at least 10GBs.
Before starting this though make sure you have a recent backup of your system. Nothing is likely to happen to it, but why take any chances?
In theory, you need only 2GBs of disk space for Ubuntu. Don't believe it. Set aside at least 10GBs. Personally, I allow at least 20GBs for any operating system. That gives me room enough for it, extra applications, and all the data I'm ever likely to be using. If you plan on doing a lot of photography or video work then you'll want to set up more space, but ordinary users won't run out of room.
Along the installation way you'll be given a choice to install Adobe Flash, I'd do it if I were you. There's a lot of video content on the Web that's in Flash format. There are other open source programs that can handle them, but Adobe Flash is the program that's most likely to play any Flash content you run across.
The installation windows will also give you the option of installing the Fluendo codec. Do it. Without it, playing music on Banshee, Ubuntu's default music player, will be a lot more trouble. Specifically, this will let you play MP3 audio.
You'll also create a separate swap partition. This partition, which Ubuntu uses when memory is tight, should be twice as big as however much RAM your PC has. So, for instance, if you have a desktop with 4GBs of RAM, create an 8GB swap partition. If you let Ubuntu set up your drive for you though, you won't need to worry about these details. Ubuntu's installer will take of it for you.
Tip: During the installation process you'll be given a choice to install Adobe Flash. Do it. You'll also have the option of installing the Fluendo codec. Do it too.
Ubuntu, on both Windows 7 and XP systems, will also automatically set itself up to be used in a dual-boot mode. Some people will tell you that you need to jump through a lot of hoops to set up Windows/Ubuntu dual-boot. Don't believe them. Most of the time, there's nothing to it. To make sure I had that right, I just added Ubuntu to Windows 7 and XP systems using Ubuntu's defaults to automatically set up the hard drive. Sure enough, it worked like a charm.
Once installed you can still get to your Windows files. The simple way to do this is to just look in Ubuntu's Places menu and click on the Windows partition. That's it. If you wanted to get techie about it, you're using a program called ntfs-config but you don't need to know that, you just need how to click a mouse button.
Since you're new to Linux you may not know what program to use to do what. Fortunately for you, the handy LinuxQuestions Web site includes a listing of Linux software equivalent to Windows software. So, for example, if you use Corel Draw or Adobe Illustrator, the Linux program you'll want to try in their place, which comes on Ubuntu by default, is Inkscape.
I'd add two things to that list. First, regardless of operating system, I've been finding Google's Chrome is the best Web browser around. Also, since it looks and works the same on Windows and Ubuntu it will make it even easier to switch back and forth between desktops. The second is that as far as I'm concerned GnuCash is the hands-down best Quicken replacement for Linux.
If there are some programs that you really must have the Windows version of, you can, of course, always just boot into Windows. If you'd rather use it inside of Linux, Crossover Linux makes it easy to run many common Windows programs in Linux. Crossover is based on the Wine open source project. You could use Wine to do everything that CodeWeavers Crossover Linux Impersonator, or Crossover Games, does, but I wouldn't recommend a Linux beginner try it.
Need more help? There's a free, albeit slightly dated, Ubuntu manual available online. There's also other online documentation and lots of free community support. If you can't find help there, or you prefer traditional support, Canonical also offers paid technical support for both individuals and businesses.
Of course, if you enjoy Ubuntu, as I expect you will, you may find yourself becoming a Linux expert faster than you might think. Have fun!