Now by the sounds of it you've got a lot of stuff in your comp, check your temps man, might be overheating. I know that for HL2 if your system ain't cooled properly during those loading sequences your comp's likely to die on ya. Since you have asus, it has somekindof heat temp measuring program you could use, otherwise you could just google a program called speedfan. It's free, it's sweet. If your temps are above 50ºC then start to worry, if they're idling at over 60ºC? then cooling's definately your issue. Make sure you also don't have your comp inna suffocated place. Inna cabinet is out of the question unless you have a big fan in there. Pretty much big fan anywhere is good.
Other than this? your comp settings should be fine man, big psu.. dunno if enermax is anygood though.. also could be drivers man, keep your vidcard up to date and your soundcard, especially soundcard as I've noticed the sound blaster audigy's aren't as strong with drivers as their older vidcards.. infact, I've tried the latest drivers with my audigy gamer, and my sound starts to CRACKLE and POP like crazzzy. Yeah, remind me to use onboard sound next time n' save my cash... anyone wanna buy a sound blaster audigy gamer? it comes with DeusEX GOTY edition and Giants Citizen Cabuto?