1. reseat your video card
2. pull out one stick of ram and try to start if it doesn't start put it back and pull another stick
until you have tried them all.
3. do you have another video card or a friend to see if it boots up?
4. failing hard drive , failing ram , bad video card . operating system is bad .
5 can you boot in the bios? if you can try and format c: drive if it cant find it failed hard drive
6. cant boot to bios two things bad stick of ram or bad motherboard. id say ram first.