About BSoD

Why does BSoDs happen? I read that it’s due to registry kits being damaged and corrupted. I don’t know what registry kits are, so can someone explain to me?
When I get a BSoD while talking on Skype, it says SPC500NC.SYS. So I searched from Google to find a solution to fix it and found a few programs that said to fix it, but they were all trojans.