I have a clone computer that, all of a sudden, will take 2 or 3 minutes to fire up. I know that this is going to happen when I turn the computer on and the DVD light comes on right away... otherwise all works normally.
So, when the DVD light comes on (right away), I can wait 2 or 3 minutes and then things fire up... sounds like the hard drive starts and you see the video screen then the bios, etc.
If I unplug everything (HD, CD and modem) the same thing happens (except that you don't see the DVD light right away). It will take 2 or 3 minutes and then you see the video and bios screen and then HDD failure.