backstory: 2.5 yrs into my 4th Mac (1.33Ghz MINI), after 2 inexplicably self-correcting week long shut downs (plus still using my reliable but anachronistic G3), Ive window-shopped these Ext HDs as both a future remedy to rescue the MINIs HD & a G3/G4 link allowing me to startup/run the G3 with it? Qs: 1)Dont HDs need cooling systems--only the mock mini 'Stack' models mention fans? Does an independent power source just prevent port overheating or protect the HD? or is temp control not an issue? 2)Can all 2.5 SATA Ext HDs be switched/swapped out? 3)Can I boot up from/work off the OS on an Ext HD? 4)Are there functional differences between Ext 2.5 SATA 'Portables', 'Desktops' & HD-less 'Enclosures'? Or will all serve my purposes?