If you have the install-restore DVD disc set you could try several things, to include an archive/install where the old files are still there but the installer puts a new OS (former system is disabled, newer install runs the Mac) or you may be able to see if running a disk utilty from the booted OS X install disc can see if the drive is repairable without having to erase/install a whole new system.
If the hard disk drive is failing, as they are known to do after a few years of moderate to intense use, that may the cause of corruption; so a replacement could be an answer. Troubleshooting can take on several paths, some of which are not necessarily joyful; plus actual replacement can be difficult.
Some of the options depend on your experience and the available software tools you may have on hand, or can have access to use. A tech-savy friend who knows these well, could also be a great help. Could you post a bit more information on detailed info regarding your computer build model/year, system installed, and so on?
Good luck & happy computing!