Hi m8
all you had to do was go to WD's site and all your questions would have been found. Here are the extracts:
General Information
Whether or not a given system can support 48-bit addressing (drives over 137GB) is dependent upon several factors. The operating system must support the higher capacities. Windows 98 and higher will support the drives with the proper BIOS, EIDE controller, and driver support. However, since motherboards and BIOSs vary widely, the answer is not as simple as making sure your operating system will support the drive.
Systems which do not support the full capacity of these drives, will generally report the capacity only up to the 137 GB limit. Any capacity above this limit will neither be recognized nor displayed. If your system is capable of supporting the full capacity of your drive, it should be properly displayed in either the CMOS set-up or during Power On Self Test (POST) prior to booting.
The motherboard BIOS, the EIDE controller, and the EIDE controller drivers you are using within your operating system must support the drives as well. It is best to contact your motherboard manufacturer to determine if your motherboard, BIOS, and EIDE controller drivers support drives over 137GB.
Another possibility is the use of an add-on EIDE controller that supports 48-bit addressing. We sell PCI EIDE controllers made by our Technology Partner, Promise Technology, on our Online Store.
Recommendations
Once the hardware limit has been overcome by using an updated BIOS or a controller card, then specific drivers must be loaded so that your version of Windows will allow for the safe use of any capacity above 137GB. Without these specific drivers, there is a definite possibility of data loss. The Data Lifeguard Tools version 10.0, in conjunction with the Promise Ultra 100 TX2 controller, and the proper drivers for the card, will allow Windows 98 Second Edition and above to utilize this space properly.
If you will be using Data Lifeguard Tools 10 to copy data from an old drive to a new (larger than 137GB) drive, assure that each drive is attached to the same Ultra ATA 100 controller card. Otherwise, you will not be able to copy the data successfully. If your system BIOS supports the drive and you are not using a controller card, both drives may be connected to the motherboard.
Common Issues
There is some risk to your data if you use a drive that is larger than 137GB and your system does not support it properly. Once the operating system has used all the bits that it does support to access the drive, it may begin writing over data that already exists at the beginning of the drive. If the operating system files are overwritten, the operating system is rendered unbootable and inaccessible. Drivers or Service Packs for the operating system are necessary to overcome this issue.
It is important to realize that the reported capacity of a large drive may often appear as less than expected. Please remember that, depending on the particular utility used, the capacity of the hard drive can be reported in either decimal gigabytes (where 1 GB = 1,000,000,000 bytes) or in binary gigabytes (where 1 GB = 1,073,741,824 bytes). Highlighting your C: drive in Windows Explorer reports the drive capacity in binary gigabytes. For example, a WD2000BB hard drive’s capacity will be reported as approximately 186 binary gigabytes.
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Determining drive capacity can be confusing at times because of the different measurement standards that are often used. When dealing with Windows and Mac based systems, you will commonly see both decimal measurements and binary measurements of a drive's capacity. In either case, a drive's capacity is measured by using the total number of bytes available on the drive. As long as the drive displays the correct number of bytes (approximate), you are getting the drive's full capacity.
Decimal vs. Binary:
For simplicity and consistency, hard drive manufacturers define a megabyte as 1,000,000 bytes and a gigabyte as 1,000,000,000 bytes. This is a decimal (base 10) measurement and is the industry standard. However, certain system BIOSs, FDISK and Windows define a megabyte as 1,048,576 bytes and a gigabyte as 1,073,741,824 bytes. Mac systems also use these values. These are binary (base 2) measurements.
To Determine Decimal Capacity:
A decimal capacity is determined by dividing the total number of bytes, by the number of bytes per gigabyte (1,000,000,000 using base 10).
To Determine Binary Capacity:
A binary capacity is determined by dividing the total number of bytes, by the number of bytes per gigabyte (1,073,741,824 using base 2).
This is why different utilities will report different capacities for the same drive. The number of bytes is the same, but a different number of bytes is used to make a megabyte and a gigabyte. This is similar to the difference between 0 degrees Celsius and 32 degrees Fahrenheit. It is the same temperature, but will be reported differently depending on the scale you are using.
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Various Drive Sizes and their Binary and Decimal Capacities
Drive Size in GB Approximate Total Bytes Decimal Capacity
(bytes/1,000,000,000)
Approximate Binary Capacity (bytes/1,073,724,841)
10 GB 10,000,000,000 10 GB 9.31 GB
20 GB 20,000,000,000 20 GB 18.63 GB
30 GB 30,000,000,000 30 GB 27.94 GB
40 GB 40,000,000,000 40 GB 37.25 GB
60 GB 60,000,000,000 60 GB 55.88 GB
80 GB 80,000,000,000 80 GB 74.51 GB
100 GB 100,000,000,000 100 GB 93.13 GB
120 GB 120,000,000,000 120 GB 111.76 GB
160 GB 160,000,000,000 160 GB 149.01 GB
180 GB 180,000,000,000 180 GB 167.64 GB
200 GB 200,000,000,000 200 GB 186.26 GB
250 GB 250,000,000,000 250 GB 232.83 GB
