Computer help no turn on

My PC won't turn on. Haven't been able to set it up for a couple of months and so it's been sitting off in the corner of my room. I set everything up on my desk and I pressed the power button and nothing. I double-checked that the outlet it was plugged into worked and the button on the power supply was on but still nothing. I looked a little bit into it and saw people saying it might be the CMOS battery dying so I changed that and still no dice. I was wondering if you computer wizzes had any other things to check that might be causing this. Thanks in advance.