I have only done raid setups with asus boards so this may be different for you. But i have booted many time with 1 drive unplugged by accident and nothing happened. I have even run the same array through different sata ports on the mobo and the array stays intact. But to me this sounds the board has died. Since it is old try cleaning all the dust off, i have fixed some older boards by just giving them a spray with one of those air can thingys.
Well, it occured to me last night that both the hard drives are 60gb each, but I remember from the first time it did boot that it olny listed 60gb inside Windows, not the 120 expected. apparently what seems to have happened is one of the drives failed along time ago, and as a quick fix I simply set the raid array to use the 1 hard drive and just unpluged the dead one but didnt bother taking it out of the case. (Funny cause I dont really remember any of this...but its the only thing that really makes sence)
So after unpluging and removing the 2nd hard drive the computer still does the same thing. But it doesn't make nearly as much sound(im guessing that was the 2nd HDD trying to spin up?)
after leaving the computer on for about 30mins I came back to it and there was an error! Appearntly somehow a hal.dll is missing or corrupted. So I found a program that was ment to solve and repair this problem from a boot disk. Ran said program Anddd!!......Nothing. same error *sigh*
But atleast by the sounds of it being able to detect a windows install, and start loading the OS the MOBO/power supply seem fine....Right?