Overlapping System Files: Am I Hosed?

I wonder if my Mac can read my mind. It often crashes late at night when it's time for both of us to go to sleep. Last night, it crashed just as I hit Command-S to save a big project I'd been working on.

But this time, it wouldn't reboot.

I popped in the usually miraculous DiskWarrior CD, booted from that, and let it scrub away. After 45 minutes, it reported a few errors, including two overlapping system files, mach and Extensions.mkext. I hit the button to replace the directory, and DiskWarrior threw an error message I'd never seen before:

2175: Can't replace the directory. Reboot from the DiskWarrior CD and try again.

I did, and 45 minutes later, the smaller problems had been fixed, but the overlapping files were still overlapping. Would DW fix 'em this time? Nope. 2175, try again.

I did. Twice. Three strikes down, I e-mailed Alsoft tech support. It was now about 4 a.m., and while browsing the Alsoft site in search of the error message, I discovered it was theoretically possible to copy files off the drive just before hitting the Replace Directory button. It worked! I got my project back and sent it out from another computer.

Soon after, I got a reply from Alsoft. This was the first time I'd contacted its tech support, and I was impressed with both the speed and detail of the response:

The (2175, -1) error indicates that some problem with your drive occurs when DiskWarrior attempts to fix the file overlaps. You'll have to re-run DiskWarrior. When you get the report from DiskWarrior, switch to the Details view (if not already in that view). Write down the names and locations of each overlapped file displayed or save the report to another drive. Then manually delete each overlapped file using the Finder (if possible) or another file management utility. After this, rebuild the drive once more with DiskWarrior and see if you can complete the directory replacement.

After your disk rebuild completes, any deleted files should be replaced from their original source (i.e. CD, download, backups, etc.) if you have them. If some of the overlapped files were part of the System, you will have to reinstall your Mac OS. When doing so, perform an "Archive & Install", which is available via the "Options" button presented in one of the installation screens.

There is no definitive explanation for why files get overlapped. To avoid this kind of problem in the future, we recommend running DiskWarrior more often. We suggest running it at least once every two to three weeks. Also, never run any other disk utility before running DiskWarrior.

I'm (or was) running Tiger on a dual G5, and have no idea where I squirreled away my OS disc, so maybe it's time to upgrade to Leopard. Or replace the drive. (I do have a second drive in the Mac that I could move everything to.) Or....

Recommendations?