On power up, everything runs, motherboard splash screen comes up, system will not POST,
If your system has got to a point of spash screen and that it askes you to select a boot device, it has passed POST (Power on self test). This is good news so far.
cannot enter into CMOS.
I think you are looking to get into BIOS. This is done on MSI boards (Just like my 790FX -GD70) by tapping the Delete key BEFORE the spash screen clears. I tap several times right after I push the power button until I see that drives and USB items are listing on the screen. Then the BIOS screen should appear.
You do not list a hard drive in your configuration, but if one is installed, be sure the SATA cable is plugged in securely. BIOS should see the drive if it is connected and functioning.
You do not mention an OS, so if HDD is new and no OS is installed, put in your OS DVD into CD/DVD drive and select CD/DVD: Optiarc DVD RW AD-7290H as your boot device. The OS should load.