I typically use memtest86 for memory testing, prime95 for cpu testing, furmark and unigine super position (one after the other) for GPU testing. Sometimes a borderline GPU will pass testing just fine on one, or the other, but I've never had a borderline gpu make it through both, one right after the other for 24 hours each. I use HWmonitor for temp monitoring in windows. the powersupply gets pushed plenty hard when you're running furmark and unigine superposition so those two also test that. I dont really have anything for pushing disk reliability though, with SSD'd they tend to pretty much just work until they dont.