I am starting to acquire the parts to build a gaming PC. My dad has an old Computer he doesn't use and I was curious as to if there where any dangers in reusing things like the hard drive and or power supply. I ever they are compatible but they break could this put my other new components at stake?
Those are probably the two most important parts to a computer. I'd encourage that you purchase at least a new power supply. If you're hard drive is old there is a good chance it is mechanical which in turn makes it prone to failure. I recommend getting an SSD if you can afford it or a new mechanical HD. How old is your HD?
As for the power supply, you don't want to have an old or bad power supply potentially mess up your new parts (motherboard, ram, cpu, etc..). Plus, if you want to build a gaming pc, you will have to get at least a 550w power supply, which I'm assuming the one you have is anywhere from 250w-400w.
I'd say as long as you can fit that HDD into your PC,do it,if you have a good working HDD already in your system. It's not gonna hurt your system in anyways,rather than hurting itself.
And about the PSU,please don't re-use it and add it to your GAMING PC. PSU is what supplies the necessary power to your whole PC,each and every component,a fact you maybe well aware of. So,if you use an old PSU to power your system up,maybe you won't have a problem at all,if it be good. But that thing be faulty or not good enough to power your system up,that's gonna put your whole system in danger. If overpower is supplied,there's likely a chance that your components like CPU or RAM or GPU or such things will get damaged by it. So you best go for a new PSU,and not use that old PSU,especially when you're planning a gaming PC.
Using old parts is fine, That being said, if the old parts aren't quality parts to begin with your only asking for trouble. If your old computer was a prebuilt, and not high end prebuilt, chances are that they used inferior parts, in which case you shouldn't reuse them, HDDs can be reused, even though the label may not be a mainstream brand, chances are underneath it was manufactured by a major builder, and therefore not the worst thing you could do. A cheap PSU will put wear and tear on all of your parts and should be avoided at all costs. You can pick up a decent PSU for like 40 - 50 bucks, which isn't all that expensive when you're probably looking at 100 - 200$ CPUs and Video Cards, 100$ Mobos, etc. etc.