I built myself a custom computer about a year ago, and everything's worked fine up until today. My stock CPU cooler for my i3-2100 was always a bit loud so I ponied up and bought a replacement for it - a Cooler Master Hyper 212 Plus.
I also orded an anti-static wristband, and made sure to read up on how to properly remove thermal paste, reinstall it, and how to install the specific heatsink.
So... all is well, the installation is a breeze, I'm grounded the entire time, put everything back in the computer, go to power it on, and... nothing. Absolutely nothing; no fans are spinning, no familiar 'beep', just absolutely nothing. The Power LED on the Motherboard IS working (and lit up), but pressing the power button yields absolutely nothing.
So I checked the connections from the PSU to the motherboard, video card, HDDs, etc. and everything is just as it was - everything's plugged in fine. I checked the motherboard, there's nothing (visible) to indicate that it might have shorted.
Is there anything else I should be looking at/testing/doing? I'm sort of at a loss as to what could cause nothing to work.
CPU: Intel Core i3-2100 @3.1GHz
PSU: Rosewill 630W 80+ Bronze
GPU: Asus GTX550 Ti
Mobo: Asus P8H61 LE/CSM
Case: Antec Sonata III
RAM: 8Gb (2x4Gb) G.Skill Sniper @1333MHz
Cooler: Cooler Master Hyper 212 Plus
HDD: Seagate AS Series 1TB
Sounds strange, you made sure the CPU cooler fan was plugged into the cpu fan header? Also, Rosewill PSU's are not well regarded but I do not know what you could have mucked up simply changing the heatsink with regards to the PSU, you could take the cooler off and check your CPU pins for damage.
two things...when you pulled the heat sink off it may have pulled the cpu off the mb pins. try reseating the cpu..the other thing to check is the back plate. if it metal is may be shorting out the back of the mb. some heat sink have a foam pad that needs to be in the middle of the mb and back plate.