Hi Sarah
First off, Welcome to MR. If you will make your thread titles relevant to the question that you are asking, you may get faster and better results.
Also it will help immensely if you detail which G3 Mac you have, and what version of OS.
If the Archive and Install is stalling half way through, then you have a problem, possibly a dying hard drive.
Before you do ANYTHING else, you need to back up your files, pronto.
The best way to do this, assuming your machine has a Firewire port, is to get a Firewire external hard drive. Stop what you are doing and go to the store and buy one if you have to. Your files are worth more than $150 to you, I will bet.
Back from the store? OK. I would go ahead and install OSX onto the Firewire drive, then boot from that. Then, back up EVERYthing from the internal drive to the external, into a folder called "Backup of Internal" (that is, don't copy your original System, Users, Library etc over top of the stock ones that the OS install disk creates on the external). If it gives you occasional warnings and errors, click Continue. BUT if it stops copying saying a file could not be copied because of an actual error, beware; it will not copy the rest of the items in that folder, or the folders that you had dragged, it'll just stop. You then have to open the folder(s) and manually drag the contents over, checking that each one has made it other than the file(s) that it chokes on (those ones are probably lost).
Then, you can proceed to either repair or to reformat and restore, the internal drive.
When you boot from the Install CD, under the Installer or Utilities menu at the top, there is Disk Utility. You can use this to verify or Repair your hard disk. That would be the first step.
Your machine may also have an Apple Hardware Test disk or this may be on the OSX CD (it will have instructions printed on the CD Label.) You can follow those directions and boot into the Hardware Test to see if it flags anything.
