Seriously though, grab a live CD, boot it up and start getting a feel for things. With many of the different distributions out there, the install CD lets you boot into a fully working environment without installing anything to your hard drive, so can have a play and see what it is all about without any risk. http://distrowatch.com/ is an index of different distributions and their popularity. Can't claim to have used it myself, but Mint seems to be pretty popular these days. Ubuntu is probably OK to start with as well, but they are doing a lot of experimental things, so don't write off Linux based on any one distro! Try a couple of different ones to see if it works with you. Part of the beauty of Linux is that it can be very heavily customised and is very flexible, but also means if you're inexperienced you may have to try a few different flavours to find one that works for you without tweaking it.
