Q:
A: it can be tricky to diagnose, but usually the computer freezes when you are working on it, and you dont receive a blue screen, just a total freeze that requires a hard reboot. also, often a computer won't POST (initialize all components) when you turn the power on, or it will take a few times of switching it off and on before it finally boots into windows. Sometimes it will crash before completing the boot process. if you think it is underpowered, you can also run a video card benchmark such as 3Dmark and you may receive lockups/artifacts/reboots as your video card draws too much power. if you are advanced you can also download a program like MBM (motherboard manager) and check to see if the voltages on the 5V and 12V lines are stable.