It is more of a marketing ploy for Hd manufacturers.
While 1Kb is 1024B, 1Mb is 1024Kb and 1Gb is 1024Mb in base 2 (what the computer uses), the manufacturers use base 10 (i.e. 1Kb is 1000b, 1Mb is 1000Kb and 1Gb is 1000Mb) to advertise their hard drive capacities.
As such, the advertised capacity will always be lower than the formatted capacity.
That is something completely different and you must be using an OLD motherboard/OS to run into that problem today.
Back in the day, ATA devices only supported 28-bit addressing and thus were limited to 137Gb in size.
This limitation is also artificially imposed by some operating systems.
See if you can get an updated BIOS that supports 48 bit LBA from your motherboard manufacturer.
If you BIOS already supports 48 bit LBA, see if you have to enable it in your OS. Here seem to be a good resource for information regarding this issue.
Actually, I built this about a 1 1/2 years ago. I installed the ASUS M2NPV-VM motherboard and the drive is a SATA 320GB 7200 RPM Segate. I just upgraded the bios and this computer has XP Pro SP3. In the bios, it recognizes the drive as a 320GB. However, when you look at the drive size in XP, it's only showing 137GB. Must be something simple I would hope.
Did you install Xp from a pre-SP1 disk?
As support for drives over 137Gb was not added until SP1, the base install would have set your Hd to its current size.
You should be able to use a program like Partition Magic to extend your partition after SP1 has been installed.
There are also several free Linux based options but they will take a little knowlage to use.
Another way to do it would be to Slipstream SP3 into an install disk and reinstall Xp.
Well I did what www.48bitlba.com said to do:
"To enable EnableBigLba in the Windows registry, perform the following steps:
Start a registry editor (e.g., regedit.exe). In Windows, click on Start->Run, enter "regedit".
Navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\atapi\Parameters registry subkey.
From the Edit menu, select New, DWORD Value.
Enter the name EnableBigLba, then press Enter.
Double-click the new value, set it to 1, then click OK.
Close the registry editor.
Restart the machine for the change to take effect.
With EnableBigLba Tool:
Use EnableBigLba tool to test and set EnableBigLba in the Windows registry without having to do it manually with the regedit tool."
I ran the EnableBigLba test tool and it said it PASSED and nothing needed to be done since I have SP3? It's still showing 137GB.?
Ensuring your BIOS is upgraded to support 48-bit LBA and that Windows also is updated are all the right things to make sure you can use large HDD's in future. BUT if your HDD originally was Partitioned and Formatted in a system that lacked that support, just changing the mobo BIOS and Windows is not the complete solution. If that is the history, then you have a 320 GB drive with one primary Partition of 130 GB and a bunch or Unallocated Space. To verify this, click on Start, then RIGHT-click on My Computer and choose "Manage" from the menu. In the left pane of the new window expand Storage and choose Disk Management. On the right in the upper half you'll see all your drives currently available for use. Below that in another scrolling window will be a list of devices that also will show you anything you can't use yet. Look at Disk 0. It probably is subdivided into the C: drive of 130 GB and another Unallocated Space of about 170 GB. If yes, you have maybe three routes to choose from.
1. Right-click on the Unallocated space and follow the menus to create a second Partition in this space, using all of it, for data only (not bootable). When that's done, use the menu again to format this new Partition using the NTFS File system (if there's a choice). When done, reboot and My Computer will show you a new drive empty and ready for use.
2. If you want the entire 320 GB in one continuous volume as your C: drive from which you boot, Windows itself can't help you directly. It has tools for expanding an existing drive by adding Unallocated Space, but it will NOT do that for the BOOT drive. The best path here may be to acquire 3rd party software like Partition Magic which will do that job for you.
3. If you want to expand per item 2 above, but not buy Partition Magic, there is another way using free software migration tools provided by HDD manufacturers, plus a spare HDD. To help buyers of HDD's move to new larger units, the makers give you (either on a CD with the new drive, or downloadable free from the manufacturer website) software utilities to make a clone of your old disk (Source) to your new one (Destination) while adjusting the final size. The restriction usually is that they will make the clone TO only a HDD they made - they don't care about the Source. So, what you can do is this. Buy or borrow a second HDD which has NO data on it you want to keep. Use the utility to clone your current HDD to the spare unit, ensuring that it makes the clone bootable. Shut down, swap drive cables, and reboot from the new clone on the spare drive. Now you reverse the process and clone back to your original drive, ensuring: (a) use ALL of the available space (320 GB)); (b) make the partition bootable; and (c) use a NTFS file System (for large drives). When done, shut down, swap drive cables again, and reboot from your original (now much bigger) drive.
IMPORTANT: First time I did this I ran the software utility from the CD supplied, and it did not work. That is because the software had no knowledge of the ability of the Windows XP version I had on the HDD, so it refused to go over 130 GB. The solution is to INSTALL the software utility on your original HDD and run it from there. Then it will know your Windows has 48-bit LBA support and will do the job properly.
Thank you so much for taking the time to explain the fix for my problem. I did install Partiton Magic and with two clicks, it added the Unallocated space to Drive C: and now I have the entire 320GB hard drive available.