Assuming that the data you want to preserve all lives in /home, Yes, you can freely reinstall any Linux distro you want without fear of killing the data you want to save. The critical step of course is that you have already established a separate partition for that important data, that you use a consistent file system, and that during the partitioning exercise, you do NOT format the partition that contains /home. (To play it safe though, Yes, it's an excellent idea to backup that important data before starting anything)
To illustrate, let's assume that all critical data will live in /home. If so, give /home its own partition, and create any other partitions as you see fit. Later, when you decide that you'd like to either reinstal or give another distro a tryout, it's basically a piece of cake to reinstall "around" the /home partition. The 3 critical steps (again) are to continue to use your existing partitioning scheme, to use the same file system (ext3, reiserfs, etc) and to NOT format /home under the new system. The result of this approach is that the contents of /home remain untouched, but all the other partitions such as /, /usr, /var, etc will be rewritten under the new distro. It's pretty sweet, and yet another advantage over Windows.
Personally, I've decided on a standard partitioning scheme, and have on more than one occasion have installed a different distro "around" my existing /home directory. As you can guess, the key is to just use the same partitioning scheme all the time, and to *not* format /home, and this practice has been super helpful to me anytime I want to experiment with new distros. Sorry if this post sounds so repetitive. Good luck with it -- J.W.
Last edited by J.W.; 04-18-2005 at 02:14 AM.