I have an extra hard drive with the system installed. When my machine crashes, the first thing I do is swap out the hard drive. If it boots, I know the crash was caused by my old drive and I mount it in an external enclosure, scan it for viruses and if clean, I scavenge all needed data from it.
If the machine still doesn't boot, I know it's a hardware problem. I usually fix these myself, but if I didn't do so, that would be the time to leave the empty bootup hard drive in place then take the whole computer to a shop for repair.