I started getting frequent disk read errors on bootup maybe 3 months ago... it wouldn't happen every time, and it would stop happening if I left my PC turned off for a while.
Two months ago I replaced the hard drive and it STILL happened after about a week. Last month, I replaced the HDD AGAIN, as well as the motherboard, CPU, and power supply. Just last night, disk read error.
I'm almost certain I've narrowed the problem down to bad, old electrical wiring in my house with my appliances and my electronics being on the same fuse. I frequently get brownouts where the power dips and the lights dim for a second or so. I just ordered a voltage regulator/line conditioner from APC, so we'll see how it helps.
My main question is, do you think my new hardware is permanently damaged, or do you think they'll be fine once I get the power under control? The fact that after letting my machine "cool down" it stops gets disk read errors makes me hopeful that the new HDD isn't really fried, but I'm not sure.
Having stable line voltage is very important as is surge protection. If you are having voltage swings, make sure the UPS you get has both over voltage and under voltage protection. That way if the voltage increases, it will reduce it to 110 volts, and if the voltage drops, it will either go to battery or bring it back up to 110 volts.
The other point you mentioned is you have no disk errors if you let the computer coold down a bit. That speaks of a heat problem and you should make sure you have adequate CPU cooling and fan cooling in your computer. Most MB BIOS screens will list the CPU and MB temperatures in real time, or you can download one of several apps (like HWMonitor) that will monitor the temps on the desktop till you know they are or aren't a problem.
Might consider trying your computer on the UPS before sending it all back, and if the problem is resolved, it saves you the hastle of RMAing components.