So after unplugging my desktop nearly two weeks ago and taking it over to my parents' place last week, it turns out my desktop is alive! I guess there might just be a short circuit in one of the USB ports which was causing it to turn off abruptly, so I just have to make sure not to use that particular USB port. I will be looking for a new power supply though just in case that is the problem - and maybe looking into more detail about what should be replaced. Then again though this desktop is 10.5 years old and I'll probably be looking into a replacement at some point, leaving this one as a contingency unit.