i might go on to mention that problems may arise if a GPT formatted drive is installed into a system that doesn't support it....
for example, an external USB drive formatted under Win7, then connected to an XP machine :icon_eek:
i learned this the hard way - lol
the GPT format allows the first sector to be a protective or legacy MBR record
the "real" GPT tables start on the next sector
so, let's say we GPT format a drive under windows 7 at 3 TB
now, we connect it to an XP machine
it is "corrected" to a very small drive
you reconnect the drive to the windows 7 machine, but the new "corrected" size is in force
you just lost a shit-load of data