I'd strongly recommend replacing that PSU with a newer unit such as the Antec EarthWatts 380D Green. You see, newer motherboards require a 24-pin ATX power connector, but that old True380 has only a 20-pin ATX connector. Second, those older Antecs used a bad choice of internal capacitors: They are loaded with Fuhjyyu capacitors that could not withstand even moderately high temperatures. Worse, the old Antecs set their cooling fans to only spin at full load, resulting in the PSU's internal temperatures that were murderous to those Fuhjyyu capacitors. The end result is a PSU that can die out on you much earlier than anticipated.
So, at the first sign of a squeal coming out of that True380 PSU itself, it is very likely to die out (and often with a loud pop). Replace it immediately, in that case.