In my last thread I asked if the PSU I chose, the Corsair CX430M would work in my pre-built PC, and apparently the answer was yes. I tried it out, and when I tried to boot, there wasn't a POST beep as there normally would be, but the HDDs seemed to be running, the fan on the GPU was working, as was the CPU fan and case fan. All my connectors (24-pin ATX, CPU 4-pin, SATA powers, PCI 6-pin, front-panel lights/card reader) were properly connected, so why wouldn't it boot?
After thinking about it I think my PSU is defective. I can still put the old parts back and my machine works perfectly fine, so that rules out any issues with the board. As I said before, everything looked powered but it wouldn't boot, so I suspect the CPU isn't getting any power.