My old iMac dies three times a day, spinning wheel, etc. I think the HD is dying. This has been going on for a year now. Bit surprised it hasn't completely died to be honest. I have reinstalled everything a couple of times but that doesn't seem to make any difference. Can I run it off an external HD? Boot it, etc? It seems that should be possible according to a few forum posts here and there. Is that true? Does the machine not need the internal hard drive for anything?? Thanks.