Thanks for responding so quickly.
The Aspire was several years old and has lived through at least three motherboards. This *was* their signature model with the clear case and uv-reactive cable sheathing. Oh well.
The replacement was a Thermaltake TR2 430NL1NH. An identical model, ordered at the same time, is performing admirably (as was this one) in another tower. Had to open the case because the old grey matter couldn't remember when I made the first post.
BTW, the RAM is AData, ordered new from NewEgg (I think). The three hard drives are all 1TB models from various manufacturers.
The mainboard and processor were purchased from an Anandtech member. I believe those items are not to blame. Call it a hunch.
I'm hesitant to throw my Antech PSU in there. Don't want to kill it! It came out of an Antech Fusion HTPC case and is about 400 watts or slightly more.
If I don't fix it I'm going to upgrade after I save up some money.
Barry
I have one of Aspire's "premium" PSU's...it was crap the day it was new...and only got worse with age. Poor voltage regulation was only one of the issues...but it got me by for a while. As soon as I could, I replaced it with a Corsair. When I dug it out for temporary service powering my old build when I stole the Corsair for a new build...the Aspire burped enough to power the case fans for a second...and died. I haven't replace that PSU yet, so I still don't know if it took anything with it when it went...but it's very possible.
Your Thermaltake is HEC built. It's OK, but only OK. Definitely not a top-tier unit. Your Antec SHOULD be much better build quality.
Unfortunately, there's no way to troubleshoot your system over the internet...so I can only make some suggestions for you to try.
First...use a paperclip to test the Thermaltake PSU. You want to jumper between the green wire on the 20/24 pin connector and any black wire in that connector. Most likely, the fan in the PSU won't start if it's thermostatically controlled, so hook up one fan to a molex connector. That way, you can tell if the 12v portion of the PSU is working. (it's not an infallable test, but should be a good indicator to the PSU's status.)
IF it works, then, IMO, the best way to troubleshoot the system is to take it apart and rebuild everything on a piece of cardboard sitting on a desk.
Start with ONLY the CPU, CPU fan and heatsink, ONE stick of RAM and your video card. IF the system boots to the BIOS, shut down, add your boot drive and try again.
IF your drive is recognized in the BIOS, Swap sticks of RAM.
Try again.
IF that works, add one more stick of RAM in the slot for dual channel.
Try again.
If you can boot to Windows, shut down and add your optical drive.
Continue until you either have a failure to boot or you get everything connected.
Then, IF everything works, reassemble it all in the case.
Yes, it's a terrible PITA to go through all this, BUT, in my experience, it's the best way to troubleshoot hardware problems.