Your files will be left alone by a system reinstall.
DiskWarrior is a commercial application made by Alsoft
- I strongly recommend its purchase. Put the CD in your drive and start up holding down the 'c' key.
Before buying DiskWarrior, try booting from the CD that came with your Mac - a restore or sytem disc (put in CD, reboot, hold C until the system begins to load).
From there, run "Disk First Aid" (in the Utilities folder on your CD). It may be able to fix your problem, but I doubt it.