If you want to dip your toes into Linux without carrying out a full installation you could do is install Ubuntu 8.04.1 using Wubi http://wubi-installer.org/
You keep Windows as it is, Wubi only adds an extra option to boot into Ubuntu. Wubi does not require you to modify the partitions of your PC, or to use a different bootloader, and does not install special drivers.
Wubi keeps most of the files in one folder, and if you do not like it, you can simply uninstall it as any other application.
Another possibility is running a Linux LiveCD. There are a whole host available. Worth considering are
Mandriva 2008.1 Spring http://www.mandriva.com/
SimplyMEPIS 7.0 http://www.mepis.org/
Ubuntu 7.10 http://releases.ubuntu.com/7.10/ (My Preference)
Ubuntu 8.04.1 http://releases.ubuntu.com/hardy/
Linux Mint 5.0 http://www.linuxmint.com/
OpenSUSE 11.0 http://software.opensuse.org/
All the Linux flavours listed above are easy to install and easy to use.
If you need any help or advice please do not hesitate to email me (see my profile)
LUg.