I haven't a clue, but I'll be happy to bump this cuz I'm not liking the sounds of Vista, either...
Seems I've heard folks discussing this.
I'm running Fedora and I love it -
http://fedora.redhat.com/
I hacked my husband's HP Pavilion laptop, cleaned out the Windows and set it up; I'm not a *real* techie so if I can do it pretty much anybody can!
It's got KDE and Gnome desktops, with an intuitive setup, but I especially like being able to open it up and tweak the code. I do believe you can burn it to CD and run it from there, but check the website to make sure.
I run it with FireFox and that makes me a very happy geekette...
Knoppix
You could run VMware Server on Windows XP and then run whatever distro of Linux you want to try it out.
I'll agree with the Knoppix post earlier I've used knoppix in the past and it's a great distro, but I really like ubuntu now (they offer a live cd to boot from the cd and then install if you want -- it'll walk you through setting up the partition, etc.) and I have just set up an open suse sandbox at work (using VMWare -- there's another great way to play with and learn linux)
http://www.ubuntu.com/
http://www.vmware.com/products/player/
http://www.vmware.com/vmtn/appliances/directory/cat/45 (get a preconfigured linux distro to run inside the vmware player)
Give it a try, its awesome... But, if you want Linux...
Try PCLinuxOS, Mepis or Sabayon.... www.distrowatch.com
Linux Mint is also very good... give that shot...
What kind of hardware do you have that you want this linux on?
ping
If you don't like Windows, I'd strongly recommend getting an Apple Mac, Linux is a step backwards not forwards. If you want something you can tinker with under the hood, stick with the American original, Unix, not foreign clones like Linux. Try Sun Solaris or PC-BSD, here's all you need to try them out, so long as you have 512Mb total system RAM:
http://www.vmware.com/download/player/
http://www.vmware.com/vmtn/appliances/directory/420
http://www.vmware.com/vmtn/appliances/directory/71
can also be interesting. Both try to run in memory and can be quite zippy.
For what it is worth, there's a good list of distributions at distrowatch.com.
Try Mepis, Linux Mint(the New beta), And PCLinuxOS(The New beta, or by then the final will be out... ) www.distrowatch.com
BTW, I've been playing with Linux distros since 1998, and Kubuntu 6.10 is the first that just installed and ran. Even SuSe 10.0 did weird things with the display during installation (which made it difficult to answer the questions), though it seemed fine once installed.
I used to keep a Windows machine in the office (Win98) but no more.
I'd have to say Ubuntu. You can run it as a live CD and then once you are running it as a live CD you can choose to install it to the hard drive. If your hardware isn't quite good enough to run Ubuntu at a great speed, then you may want to try Xubuntu, which uses XFCE instead of GNOME (XFCE is less memory-using than GNOME or KDE).