Mel
You have two separate issues.
1. The difference between hard drive manufacturer's advertised disk capacity
and the capacity seen by XP.
2. Large disk drives not being fully recognised by XP.
ISSUE 1.
You are not missing any space, although the drive manufacturer could be
clearer.
In XP, open My Computer, select the appropriate drive and right-click,
select properties... beside 'capacity'
you will see the total number of bytes on your disk and to the right the
number of Gigabytes.
For example, on my 40 Gb 'data' disk I have 40,007,729,152 bytes... which is
also listed in disk properties as a capacity of 37.2 Gb.
The Hard Drive manufacturer refers to the 'bytes' total in my case as
40 Gb... and, in
purely decimal terms, it is - 40,000,000,000 bytes.
The 37.2 Gb is what the operating system (XP) 'sees'... because the OS
calculates
1024 bytes as 1 Kb, 1024 Kb as 1 Mb, and 1024 MB as 1 Gb.....
so in my case 40007729152 / 1024 / 1024 / 1024 (that's bytes => Kilobytes =>
Megabytes => Gigabytes) is 37.2 Gigabytes as far as the computer is
concerned.
Neither calculation of the disk size is 'wrong' ...... they are equivalent.
In your case the drive capacity - approx 80,015,458,304 bytes - will be
referred to by the computer as 74.52 Gb. (The drive capacity may only show
the first 3 digits.)
ISSUE 2.
Have you installed XP Service Pack 1?
Check here for further details.
"How to Enable 48-bit Logical Block Addressing Support for ATAPI Disk Drives
in Windows XP"
http://support.microsoft.com/default.aspx?scid=kb;en-us;303013
Hope that helps
Pete