My 13-month old XPS 8300 will not boot. When I hit power button to unhibernate, it will begin the boot proces. It will display the Dell XPS page and then screen blanks and I get a blinking underscore symbol in top left corner of monitor. However, typing on the keyboard has zero effect on the underscore. The power button is still white. There is a single lit LED (orange) near the RAM boards. I can see no other diagnostic leds. The rear fan and processor fan are running.

XPS 8300: intel i7-2600, 8GB SDRAM, AMD Radeon HD 6450 w/ 1GB DDR3, USB3.0, 1TB ATA HD, 16x DVDRW, Windows 7 Home Premium

Any suggestions would be appreciated.

Thanks