Windows 98 crashed Says No OPS! HELP!

Hey all on my kids computer he did something of course hes a kid so he has no idea what! But anyways when we start it up it says no operating system. I tried to load the windows 98 cd but it starts then a little way on it says there is an error because it does not have a hard disk or there is a problem with the hard drive. Well we had 2 hard drives on this machine so we disable the orginal and pulled in the 2nd one and it still says the same thing. Im at a lose on what to do.... Any ideas???????? THanks