Interesting technote to read from Apple – they are changing the way that Mac OS X 10.6 reports the size of a disk. In the past, they have used 1MB=1024kB and 1GB=1024MB, but now in line with standard SI Units, they are using 1MB=1000kB and 1GB=1000MB. This is more in line with the measurements that disk manufacturers have been using for quite some time and will help explain why that 1TB disk you installed only formats up as 900-odd GB.