Still sounds like an overheating problem. Is the CPU heatsink OK?

I agree. My gut tells me the CPU is faulty.

TypoBoy, my APC does include voltage regulation. Backup battery will intervene if AC utility voltage goes above 136 V, or below 90 V. (I can change these numbers.) Every time I check it, it says the current voltage is 115 V.

The last transfer to battery was caused by electrical noise, which lasted under 5 seconds; the one previous was a blackout, also under 5 sec; both I believe were related to thunderstorms.

how to check on either the heatsink or the possibility of a motherboard temp. sensor.

Checking the heatsink requires opening the case. The temp. sensor and contol setting in my (five year old) machine can be accessed through SETUP -- before Windows loads. I can get to SETUP by holding DEL during boot-up, but that may not be how it works for your machine.

But if it were overheating, wouldn't it have done this at Best Buy or my old place, too?

Maybe, maybe not. There are too many "it depends" variables. Was it on a cool counter? Was it kept upright? On its side? Things like that, and you have no way of knowing.

Sorry to post & run, but gotta get Dad to the airport....

Eddie, can you or your gut tell me how I, who know nothing, can find out if something's wrong with the CPU? Maybe I just need to get a private geek in here to look at it. I'm not taking the blasted thing back to Best Buy; they've had their chance.

Sometimes when it restarts, it tells me it needs to check the disk, but it never says anything's wrong with it after it does the scan.

Turn off the computer andopen the case. Make sure every single connector and cable is firmly in place as well.

After that, leave the case open and turn it on. Check to see that every fan, including the one in the power supply is spinning.

Then shut it down and put the cover on and run it for a while.

If it still turns off randomly, try running it with the cover off, that would keep it cooler. maybe have a fan pointed at it.

if it's a cooling issue, the mysterious shutdown shouldn't come back. If it does, it is possibly a failing CPU chip/card.

I will do that. Thank you.

Actually on modern case designs running them with the case open actually makes them run hotter. The fan systems are specifically designed for airflow across components to pull the heat away.

I'm in the market for more RAM for my G5. Dealram pointed me to Omni Technologies as having the current best price for what I want.

So, two questions. First, "2GB (2x1GB)" means 2 sticks of 1GB each, right? Second, does anyone have any experiences with this vendor? Good or bad?

Zenkitty, the other problem you may be having is that your power supply may be bad, or too small to support all the hardware running on your computer. Your problem sounds suspiciously like one I had, and power supply was the answer.

I'd be particularly suspicious if it turned out that the "seemingly at random" turned out to be "every time a CD or hard drive has to spin up." Spinning up a drive is one of the heavier strains on a power supply, and if it's bad, that's a common time for it to fail.

So I probably will get another drive for the Tivo within 4-6 weeks. Should I add another drive, or replace the drive I have?