If the HD has a bad sector, it read to that portion and freeze everything. Since you run and didn't flag any errors, then it's not HD. But I'm just speculating that this might be a Power Supply power overload causing other component to receive excessive watt power, which can also freeze up. However this is fairly new power supply, so there is hope you can fix it before trying new power supply. Anyway what is your audio card brand? are you using integrated or dedicated sound card? Go to start, type in dxdiag. Run down your sound card name/version in audio tab.
Also, can you do me a favor, run this to check your power as to why you can't put computer to sleep.
Start, find Accessories, right-click command prompt "Run as administrator". In command prompt, type "powercfg /requests" . It will scan and report any services are running in background that is not allowing computer to put to sleep.