I'm rather 'out of my depth' with the second bit of your question but the 'missing' space is easily explained by the rather strange definitions of a 'thousand' used in the world of computers.
A kilobyte is (according to the strict meaning of 'kilo') 1000 bytes. However, because of the way that computers operate using binary code, it's more sensible to work with powers of 2. Since 2 to the power 10 is 1024, it's that number of bytes which is used by your PC to define a kilobyte, rather than 1000.
Following the 'strict' definition of a gigabyte would define it as consisting of 1000 x 1000 x 1000 bytes. However, the 'computer' definition is 1024 x 1024 x 1024 bytes. Manufacturers use the 'true' definition of a Gb but your PC applies the 'computer' definition. That means that a completely clean disk will only appear to have 93.13% of its nominal space. Which is why a 'true' 320Gb disk only has 298 'computer' gigabytes of space on it.
Chris
PS: This might help with second part of your question:
http://www.theeldergeek.com/ntfs_or_fat32_file _system.htm