When you re-formatted, you should really have run Windows in its bare state with no net connection for a couple of days, then installed trusted security software (stuff that we know to be stable) and updated the OS, left it for a couple more days, and then installed your other software.
You see where I'm going with that? By immediately restoring your installation to its previous config by bunging on all your software, you had little chance of ascertaining the root cause.
It could even be a hardware problem; PSU, motherboard, hard-disks, etc. All potential culprits.