Your best bet is to set up your computer to dual boot Linux/Windows. I set up Linux on an old 40 gb drive from a junked Compaq computer. My computer boots that disk by default.
A program called Grub is a menu giving you the option of booting Linux on that disk or Windows on its own disk. If my old 40 gb dies, the next drive in line is my completely untouched, no changes made Windows XP drive and it boots normally. So you see, there's no repartitioning of your Windows hard drive, no risk!
Want to know something that will blow your mind? My Ubuntu installation reads and writes all flavors of Windows partitions like a native. Windows cannot read or write an ext3 partition. My Linux programs read and write Windows data files just fine. I can load MS Word files into Linux Open Office.org, do whatever, save them, switch to Windows and load 'em right back up again.
The free installation understands the expensive one perfectly! The expensive one pretends the free one doesn't exist. Who is afraid of whom? Hmmmmmm?
You have to love it.