I always recommend this to friends of mine at school who want to try Linux out for the first time ever, and have been using Windows their whole tech-lives. Depending on the amount of RAM you have (512mb DDR should be enough, it always ways for me... 256 might even be ok), go to www.knoppix.net/get.php and download Knoppix. It's a Live Linux distribution, which means you download it, and burn it to a cd, and it runs off of the cd without an install onto the hard drive. The CD is obviously bootable, so whenever you want to use it, you just pop it into your cd drive, and reboot your computer (making sure to boot from the CD drive, you may have to change your boot order in your BIOS, easy enough to do), and Linux will run entirely on CD, using some of your RAM to run certain things in the background. If you have a CAT5 cable hooked up to your computer for Internet, then you should be fine, as Knoppix is as far as I know completely up to date on all Network Interface Card drivers, and it knows how to get an IP address for your computer and everything. This has always been my experience with this distribution, as well as with another Live Linux distribution called IWHAX, formerly known as Whoppix. IWHAX is designed much more for the network security professional in mind. I've been trying to find IWHAX again for a while, but it seems to have dropped off the face of the internet.
Anyway, Knoppix is absolutely ideal for someone like you, who has never used Linux before (so I gather from your post, anyway), and also I think I understand that you're not *too* sure you want it or not, so once again, Knoppix would be what I would suggest since there is absolutely no installing of software. Your Windows installation will still be there, and you won't have to sit through a nerve-wracking installation, wondering if your Windows partition will still be there (if you want it to still be there). Now, users of Knoppix have, to some extent worked out an actual hard drive installation of Knoppix ( http://www.knoppix.net/wiki/Category:Hard_drive_Installation ), but judging from what I've found there, I wouldn't recommend it. Plus, based on my own experience with Knoppix, it's just plain great to be able to run an entire operating system right off of 1 single cd, then, at a whim, taking it out and booting back into your other operating system with all your other stuff there.
Make *sure*, if you do this, you read http://www.knoppix.net/wiki/Downloading_FAQ before you do anything, it might save you some question-asking later on, and with Linux, reading the manual always saves question-asking later.
This one will save you some questions later too:
http://www.knoppix.net/wiki/General_FAQ
"MINIMUM SYSTEM REQUIREMENTS"
----- If your computer was made in the last few years, it should meet or exceed these without any problem.
Q: What are the minimum system requirements?
A: Intel-compatible CPU (i486 or later), 16 MB of RAM for text mode, at least 96 MB for graphics mode with KDE (at least 128 MB of RAM is recommended to use the various office products), bootable CD-ROM drive, or a boot floppy and standard CD-ROM (IDE/ATAPI or SCSI), standard SVGA-compatible graphics card, serial or PS/2 standard mouse or IMPS/2-compatible USB-mouse.
I hope this has been informative. Have fun exploring the wonderful world of Linux, and if you like what you see with Knoppix, by all means, move on to a real, installed distribution. Do plenty of reading on several of them before choosing one. Believe me, it pays off in the long run to read and read and read about various distributions and comparing the reviews on them before installing them. Some of them have got some bad hardware compatibility issues. Enjoy, and good luck.
Edit: Some people may say that Live distributions aren't a great way to start out with Linux, but personally it got me off to a great start. After I was comfortable with the general interfaces, how everything worked, commands, et cetera, I then moved on to actually installing a distribution. The first one I actually installed was Slackware. I had some pretty nasty sound and video card compatibility issues, but the video worked good enough, and I was able to do everything that I needed to do. After a while with Slackware, I spent the next few months just trying out every distribution I could get my hands on. Believe me, it gets addicting. Have fun.
Edited again: I didn't even notice how late I showed up in the discussion. My apologies; I hope this might still be found useful by someone :)