OK, Try adding a video card to the computer and by passing the onboard video chip. If there is already a video card, try swaping it out with a different one. Just a suggestion
You may be able to recover your data from your harddrive, by using a PATA-to-USB adapter (google for it)I wouldn't spend any money on it though, unless your data is that important....... OR, adding your Harddrive as a slave drive to known working computer...
edit: Pata to USB would only work if your drive is Pata (not SATA)