External initial release

My Dell Inspiron desktop is having a hard time booting up. I press the power button and the light flickers for literally half a second, but then nothing happens. If I hold down the power button, the light flickers repetetively as if it's being pressed multiple times.

Has anyone ever installed an SSD on this model? I have tried 3 different models of SSDs, but none of them will insert all the way, it gets stuck about half way. Regular HDDs insert just fine (I've tried several makes/models of HDDs and SSDs, and so far all of the HDDs fit, but none of the SSDs fit.