"would it be safe to put the old harddrive in the new pc to get the files?"
Yes it would be safe, but if you're not comfortable doing that, you could buy a hard drive enclosure, put the old drive in that and attach it to your new PC via USB. If the old drive is okay, you can then drag and drop the files to your new PC.
"any chance it was the harddrive that caused the other pc to crack up?"
That's possible if you were seeing or hearing some life from the old PC. If there was no sign of life, it could be something as simple as a failed power supply, or something more serious, like a failed motherboard.
I'll leave your games questions for our gamers to answer, I'm afraid I don't play games on my PC, so it's a closed are to me.