http://www.fixya.com/support/t444871-915pl_a2_no_post_no_beep_no_keyboard
Lets address the video. Display is more important.
If your only using one PCI-E you do not need to plug in the 4-pin power connector pg. 20 in manual, see notes no# 4.
However it is unclear if this is true by reading your manual.
On other boards the 4-pin 12v power connector is not needed un less you are running 2 PCI-E cards.
(You will have to test this statment).
Disconnect the power connector pg. 20 in manual, see notes no# 4.
Remove your installed PCI-E1 video card & re-seat it, (making sure it is seated evenly). (If you have a second PCI-E card do not install it.
Start PC & enter bios. Check that your bios is set to PCI-E for video display & not VGA. Pg. 32.
While in the bios disable the audio. (for now).
Set Plug & play Aware O/S, to No. (This allows the bios to set IRQ's rather than windows).
Save & re-start the PC. Did you get video? No?
Shut down the PC & connect the 4-pin 12v connector for the PCI-E1. Start the PC. Did you get video display?
Other reasons for not to getting video display.
CPU not seated correctly / bad or bent pin. Socket locking arm not
engaged. Thermal grease not applied. HeatSink not locked.
1. Video card needs cleaned. (use house hold Alcohol & cotton sawbs). Clean copper contacts. Clean out PCI-E slot.
2. There may be a short between the board & the case.
3. Connection is loose, (either end of the video cable).
4. Connected to the wrong video out-put. (Switch cable to second video out put on a dual out port card).
5. Have a bad video card. (Swap it if you got another).
Memory check.
1.Can include not correct voltage for board.
(you'rs must be 2.5v). No higher.
Over clocking memory in bios. (Set to Auto)
3. Bad DIMM. (remove one DIMM if two is installed), (swap slots in-between restarts).
4. Download free Memory Tester (click the link).
http://www.memtest.org/
Give the stuff above a try Stephen.
It's late & I'm wired.
Have a good day!