If you chose to reinstall, I would suggest to update 1 at a time. Download 10.5.5 update from Apple, patch and install. Do the same for the next. After 10.5.6 you might have a problem mounting .dmg files, check system.kext for kernel version and install seatbelt.kext (using kext helper) for that version, most likely 9.6. Continue downloading updates and don't forget to patch. Do not play with any modifier so not to screw your install.