HP Pavilion a1477c with Windows 7 HP installed. Installed brand new video card in PCI-e slot and the machine won't boot - no video, no BIOS screen, no nothing. Remove the video board and it boots fine. Checked the video board (XFX Radeon 5450 - relatively low end, low power, so shouldn't be an issue) in another computer and it works fine, so it's not the video board.
Any suggestions appreciated.