|If it boots off the onboard video but not from the graphics card, it could be the card, the power supply (marginal/minimal power on the 12Volt Rail(s)), or your BIOS PCIe settings. Check the BIOS set up for the video settings and make sure that the PCIe port is the default graphics part. If that is not it, then you will have to try swapping out the power supply and graphics card to see which may be the problem (easiest if you happen to have either or both around in known usable condition).|
Post your graphics card and power supply's detailed specs for advice related to them and motherboard information is always useful.
As mentioned briefly, a power surge or even brown out can damage a power supply and even sometimes other components. Getting a good UPS will offer the best protection from all storm and utility related power issues and the good ones offer protection from network and even co-ax cable ports to prevent storm damage through those ports as well (I once lost all home network gear and ethernet ports on all home computers when lightning struck a house next door and the surge came back through the Cable TV into my home network. I had recently bypassed the UPS cable protection and network protection in an experiment to see if it effected our internet speeds and I was being lazy and put off reconnecting them. All new router, switches, and network cards were needed.).
You have to be a little bit crazy to keep you from going insane.