Most likely you have a slave/master issue. I'm assuming that since you said its an old hard drive, its IDE/ata100. first steps, remove the hard drive and see if the computer acts normal again. second, if that solves the problem there is likely your issue. third, if you can, put the hard drive on a separate channel, this may involve removing the cable from your cd/dvd drive. plug that ribbon into your hard drive, and boot the computer. if both drives show up fine then you likely have a master/slave issue. if it doesn't show up the logic board on the drive may be toast.
Thanks djdepraved, removing the hd did the trick, there is another open slot on the ribbon I'll try that in a little while and