Check your local Craigslist or other classifieds for cheap old GPUs. Or if you have another PC, borrow the GPU and power supply just to get it to boot.

You can check the data the drive itself keeps about disk errors. This data is called SMART.

https://www.howtogeek.com/134735/check-ssd-or-hdd-health-with-smart/

Figure out if the drive is having problems or not, then look at replacing it.

Another thing that slows down old laptops is thermal throttling. Once again there are plenty of programs you can download to check component temperatures. Have you cleaned dust out of the inside of the laptop and re-done the thermal paste?