I've never updated any version of Mac OSX and have had Tiger preinstalled on my MBP. I want to upgrade to Tiger without wiping the hard drive or "archiving"... i just want a straight upgrade. how will this affect the performance? it should technically increase b/c now Leopard will take advantage of the Core 2 Duo's 64-bit capabilities... but will having Tiger somewhere in there slow it down? Will all traces of Tiger get erased? Leaving only the new Leopard OS?