Well, open the case and give the system a good cleaning with a can of air. Once it is clean, inspect the heatsink fan mounting to be sure it is secure.
Remove your ram chips and blow out the slot or slots with the same can of air. Reinstall the ram; be sure it is fully seated. Now attempt to pw ON. If the system will not complete POST, the first part I would swap would be the pw supply. Note you do not have to fully install a test pw supply. You can simply connect atx, aux/cpu, and video pw. Hot the ON button and see if the system will POST.
Remove your ram chips and blow out the slot or slots with the same can of air. Reinstall the ram; be sure it is fully seated. Now attempt to pw ON. If the system will not complete POST, the first part I would swap would be the pw supply. Note you do not have to fully install a test pw supply. You can simply connect atx, aux/cpu, and video pw. Hot the ON button and see if the system will POST.