Only Archive and Install Panther, and use no other installation methods. A bug in Panther (Mac OS X 10.3) may cause some external hard drives to lose all their data. To keep out of harms you way, you can make more than one frequent backup to external Firewire hard drives and SCSI hard drives (assuming you have built-in SCSI as some SCSI cards aren't yet Mac OS X compatible). Some early iMacs that didn't have Firewire can have Firewire added with Sonnet's Harmoni G3 card. A few Mac OS X compatible machines don't have a reliable backup medium available to them:
iMac 350 through 400 Mhz without DV ports, iBook 300 Mhz through 366 Mhz with DV ports. Those with DV ports (IEEE 1394, also known by Apple as Firewire) do have reliable backup to available to them.
While CD burners work with these, use only CD-R media (not CD-RW) and only from Verbatim, Imation, Sony, and Kodak are relatively reliable. But not as reliable as hard disks. For hard disk backup, Mac OS X has two very reliable programs: Carbon Copy Cloner and Retrospect Desktop. Some versions of Retrospect Desktop prior to current were called Retrospect Express. Version 5.0238 of Express is known to work quite well. I have yet to try Desktop, but am told it offers more licenses than the original Express version.
Other full hard disk backup utilities which may also offer good backups to Mac OS X:
Babel Company Impression
Pro Soft Data Backup
Tri Edre Backup
Firewire bootable backup is only available to those machines with AGP graphics cards built on the motherboard, or AGP slot on hard drives that use Oxford 911 chipset. Some have reported problems with Maxtor drives in external firewire cases not being bootable. The G3 Blue and White, G4 PCI graphics (links to knowledgebase article that tells the difference between G4 with PCI graphics and AGP graphics), won't boot off Firewire drives, but will off SCSI. Not all SCSI and Firewire cards are Mac OS X
bootable, check the manufacturer if it is. Dantz maintains a list of supported SCSI cards under Mac OS X. A good site to find out more about expansion cards and their capabilities is Accelerate your mac.
Repair Permissions under Mac OS X 10.1.5 and above, and boot into the Mac OS X CD, open the Installer menu, and select Disk Utility, and First Aid tab to repair the disk. Sometimes Running fsck -y will work as well. Only when you have two reliable backups, can you use directory repair utilities mentioned on this FAQ. See more tips here: http://www.macmaps.com/Macosxspeed.html