Tim asked, “I assume that if I have an unpartitioned drive with Windows installed I can’t install Linux without re-installing Windows?”
No it is MUCH simper than that.
To try Linux without installing it on your computer you download the latest version, in my case Ubuntu (my prefered brand of Linux) from here. You then burn the image to a cd (instructions how to do that here as you need to burn the image not copy files).
Live cd: You put the above cd in your switched off machine and then start it up (with usual printer and stuff plugged in). Instead of booting into windows it will load a ‘live’ cd version of Ubuntu (almost all versions of Linux do this option). This gives you the chance to see if it has detected all your hardware and will work on your system without problems. Play with it like that a while. Warning though, this is a very sssllllooooowwwwww way to use Linux. When you switch off thee computer and remove the cd it your computer will work again as though it never happened.
Wubi: Another trial option is to download Wubi from http://wubi-installer.org/. This will enable you to install Ubuntu on your windows machine like it was a normal windows programme. During the installation it will ask how much space you want to give it and you should give something like 5-7GB if you are going to use it as a trial – though some people stick with Wubi for a while. This will be enough room to save documents and files. No partitioning takes place with Wubi. Not as slow as the live cd but still slower than a real installation and some things don’t work as well.
Wubi will add a new boot menu so that when you start up your machine you will get an option to start windows or Ubuntu and you use your up and down key to choose the you press enter.
If you have the Ubuntu installation cd you don’t need to download Wubi as it is one of the options on the cd. For this option put the cd into your machine while it is running on windows and you will get the option to “Install Inside Windows”, this is Wubi by another name.
To get rid of Wubi go to you windows add/remove programme and remove it like a normal programme. Everything will go including the boot menu it added.
Dual-boot: The best and ‘real’ installation is to boot up the live cd and when you see the option to install you choose that. The installer should automatically see your Windows stuff and give you an option to allow the installer to add a partition for you automatically for Ubuntu and shrinking the one holding Windows. At this point you can choose how much space on your hard drive each can have. You will end up with a computer where you can boot up into Ubuntu or Windows, depending on what you prefer each time.
Some people even like to have thier Windows running inside a window in their Linux installation using something called ‘Virtual Box’. Google it if you want to know more.
None of the things above will mean you have to reinstall Windows.