I've seen this before. My mate had it on his box. He did two things & wasn't sure which one fixed it: He took the power lead out & the battery, then reset the bios by clearing the jumpers & renoving & re-inserting the cmos battery for good measure. He also jiggled around the hard drive & reseated the ide ribbon connector & it fired up ok.
Like I say, he wasn't sure if he hit the problem on the head or got lucky, but it worked for him.