For the better part of the past 3 years, my G4 400mhz desktop has been plagued by the (seemingly) same crash behavior. At this point I think it must be some hardware/motherboard problem. I'm running 10.3.8 with 1gb SDRAM. The crash seems to happen regardless of peripherals, and I tried taking all of the RAM out to identify a bad dimm. Crashes continued with the RAM out. One thing to note: I recall this sudden "freezing" happening when I had OS 9 installed. The mouse would just stop moving in the Finder-- not particularly tied to any app. I mention that to bolster the claim that it's hardware and not a "permissions" type of OS X issue. There doesn't seem to be any specific trigger to cause a crash, but if any sound is playing, the crash will cause about .5 seconds of the sound to loop until the computer is reset. It seems that certain "graphics-heavy" uses might cause a crash, such as excessive iTunes window resizing or placement. Also iCal window actions seem to cause a crash. The thing is, sometimes I can try to force a crash by messing with iTunes or iCal, but they'll be ok. Other times, out of the blue while using those apps, a crash will occur. The crash is rarely preceeded by spinning wheel activity-- it just seems to suddenly freeze. Sometimes I can go 1-2 days (maybe longer) with no crash and other times I crash 4-5 times a day. Regardless, I usually shut down every night. Right now I have a 120gb drive partitioned three ways. My Panther partition has approx 5gb free space. On the other partitions I might have old versions of my OS backed-up, so perhaps my current system is seeing a different system folder. One other random point: I used Applecare to replace the original motherboard about 6 months after I got the computer. I can't recall why, but I remember the tech saying it wasn't uncommon. I'm planning to get an iBook within a week, and I'm hoping to keep this old G4 to tinker with and use for something-- but not if it is beyond help. I'd appreciate anyone's thoughts or suggestions!