^ Not able to get into BIOS,this is problem
Change the sata cables, ports, sata/molex power connector. If it doesn't work despite doing all this, the hard drive is dead. See if you can get through post after physically disconnecting the hard drive from the system. If the system boots through POST without the HD connected, The HD is surely fried. If it doesn't, there could be something else that's a problem. To completely rule out whether the HD is damaged or not, connect the HD on another system and see if it gets detected on another system. If it does, boot to windows, google and download HD tune and run an error scan. If there's no corruption on the HD, the HD is safe.
To isolate and troubleshoot for the rams, google and download memtest 86+. You will get the instructions on how to run memtest with the ISO or google out for instructions. Run the test for 6 hours to completely rule out the ram's instability. If it fails, RMA it.
If either doesn't work, get an obsolete, low powered GPU, connect it and see if you can get the display. If it does, problem is the GPU. If it doesn't, it can be the psu or the DIMM slot of the mobo.
Do note that its best if you do all 3 even if you have found 1 of the hardware components is the source of the problem.
If there is warranty time left, send it for replacement. To be on a safer side for the long term, change the psu.