It sounds a lot like some of the early symptoms of bad caps (google it) which basically means new motherboard. If you still have the old HDD around, you could try putting it back for a day or two to see if the symptoms remain or vanish. It's not out of the question that the new HDD is defective.
So, my computer's been failing recently. This is what happens:
I'm using my computer, and suddenly, the screen turns black. The hard drive light doesn't blink or anything. I try to turn the computer off by holding the power button down, but doesn't work. I have to unplug the power chord from the power source. If I restart the computer immediately, it won't start, and the screen remains black. The hard drive light blinks a couple of times, and then nothing else happens. Not even BIOS screen or anything. I have to wait a minute or so before restarting it, and it boots normally.
I recently changed hard drives, and this hard drive is new, so that's not it. It's not a heating issue because this has happened 5 minutes after turning the computer on.
Any ideas? Could it be motherboard? RAM?
Thanks in advance!