I have a System I have completely stripped down, and have the MoBo, GPU, Memory, HDD, DVD RW Drive and PSU on the desk at the minute. I've went threw the full fault finding process from Start to finish. Its not the GPU, or HDD, I've replaced the BIOS Battery and I've Changed the PSU.
The fault I'm getting is the Systems BIOS is resetting it self, then no detection of the DVD Drive. I know the BIOS battery is working but I'm not sure if it is dying TBH so I'm thinking that. This is a System I have had trouble with before as I posted about it but since have changed the PSU. Previously the PSU was indicating its flashing LED, so while the Components were in the chassis I was jumping the motherboard & PSU with the PSU switched on then connecting the 24 Pin connector to the board and the System was booting.
Not sure what it could be but mabie a MoBo failure I'm thinking! ..