So I think the problem is either a loose cable connection or a faulty monitor. I swap both out but still get the same problems. That then leads me to believe perhaps the video card went (it is an integrated card). So I bought a new video card, popped it in, but still experienced the same problem. This leads me to believe perhaps the motherboard got fried somehow, even though components are still getting power. The processor fan is still spinning, the DVD drive still opens/closes, etc.
So I bring the computer back to her house, giving her the recommendation that it would probably be cheaper to just buy a new computer than to pay to swap out the motherboard and other possible components. However, when I plug it back in at her house, it boots up without a problem. Right into Windows, allowing her to use her computer as she normally would.
My uncle then tells me that it would go on sometimes, though 90% of the time, when trying to turn it on, we would experience the blank screen (with no POST or anything else). He also told me that when it does boot up, it does NOT shut off on its own or anything. It will be usable for as long as you leave it on. The only problem is when it's completely off, it usually won't turn back on.
So now I'm stumped. If the problem were the motherboard, I would think it would NEVER turn on, but this computer is turning on sometimes. I'm at a loss.
If anyone has any other suggestions--or perhaps can confirm that it might still be a fried motherboard--then I would greatly appreciate it.