It usually says a number on the side, for example 550W. Just to make sure, how powerful is your PSU (Power Supply Unit)? *Your PSU is not powerful enough to supply the added component (should only be the case if it's your GPU, nothing else really draws a lot of power). If it doesn't boot at connecting a new component, your issue is most likely one of the two following: Add one component at a time and leave useless things like an extra HDD or a sound card to last. If it seems to boot without issues (fans spinning, all lights on etc) add another component (RAM or GPU). Keep all fans connected, especially the CPU fan as it will refuse to boot all the way without a running CPU fan. If that doesn't work, try removing all components but the motherboard and the CPU. The most common problem when you've installed a new component is that you've either knocked a cable loose or simply forgot to attach a new one. Check your motherboard manual for POST beep codes for your specific motherboard. No beep or several short/long beeps can indicate hardware failure. One short beep generally means that the POST has passed and that it will continue booting. If your computer does not even pass the POST (Power-On Self-Test) it's most definitly a hardware failure.

Laptop turns on then off right away