Big cases hold more harddrives, CD-ROMs, bigger (better) graphics cards, more power supplies, and more fans!kool this all looks really kool or ye does ne1 kno y thy make pc cases so big wen thy have so much room left in them i could fit my pc into such a smaller cae and i alredy have a midi case
Oh, and you can frighten little children with them.
A PC that I built for someone earlier this year was in a massive case, it was ~50" high.
As for hard drives. To be safe, I'd soft-mount them, eg. have rubber washers between them and the case to absorb vibrations. Make sure it's mounted horizontally, as this reduces wear on the head. Also, I'd go for either a Maxtor or a Western Digital branded drive, as these are regarded as the most sturdy.