Last year I upgraded the hard drive in my computer to a 250 GB drive and also upgraded from Windows 98 to Windows 2000 Professional SP4. During the upgrade process I updated the computer BIOS to support the large size of the new hard drive. I now also backup important data to an external 300 GB hard drive. When installing the TrueCrypt application (which you recommended in a recent Tip of the Week) a message appeared saying “Warning: 48 bit LBA ATAPI support is disabled on your system. Therefore you should not write to IDE disks larger than 128 GB. If you do data on the disk may get corrupted. This is a limitation of Windows. To enable 48 bit LBA support add the EnableBigLba registry value in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\atapi\Parameters and set it to 1. For more information see support.microsoft.com/kb/305098”. Upon checking the registry this entry was absent. I added the entry, as per the error message, and now I can install TrueCrypt without encountering the warning message. I am a bit worried after this message appeared, as I have been writing to two hard drives which are greater than 128 GB before being made aware of this issue. As such, could some of my data have been corrupted?

In the first instance, this problem should only manifest itself in relation to the 250 GB internal hard drive installed in your computer. You will notice that the error message says you should not write to IDE disks larger than 128 GB. IDE (integrated drive electronics) is the bus used to connect hard drives and other internal drives (e.g. CD/DVD drives) to the computer motherboard. Since your computer is relatively old I assume that your computer is using IDE (also known as ATAPI) as opposed to a different type of connection such as SATA. This is because the issue you have experienced only affects IDE connected hard drives, rather than those connected through other means such as SATA or USB. While this may provide some comfort knowing that your backup drive should be safe, there is still a concern surrounding the data on your internal IDE hard drive which could have been affected by this problem.

Reading over the Microsoft Knowledge Base article it seems that this was a known fault in Windows 2000 that was corrected in Windows 2000 Service Pack 3. Since you are running SP4 this fault has been corrected in that update for the operating system. However, even though SP3 and above supports 48-bit LBA this still requires the registry change to be made in Windows for the support to be enabled. You have done this and support appears to be enabled on your computer, as the error message no longer appears. So, we now need to check whether you should be concerned about corrupt data on the computer.

When researching your question I found it quite interesting that the only time this message appeared for many users was when attempting to install TrueCrypt. So, it seems that you only found this problem by chance. I assume that your hard drive appeared to be working correctly before being informed of this issue, since you appeared to have successfully installed Windows 2000 and other applications on the computer, and proceeded to use these without any problems. Therefore, I am not sure how else you would have been alerted to this problem except when you installed TrueCrypt. However, if you continued to use the computer without enabling this support you may have started to notice data corruption on the drive which could have been a clue. Nevertheless, it would have been quite a jump to find the root cause of this problem especially with such a general symptom.

In any case, since you have discovered that your computer is subject to this issue and have taken measures to correct the problem we need to check whether damage has already been done. Unfortunately there does not appear to be an easy method to determine whether any data on your computer is corrupt. As such, you will likely need to play this by ear and monitor your system for any instability or data which is not reading correctly. Should you find any corrupt data you may need to recover this data from your backup drive. However, bear in mind that if you copied data from your internal hard drive to the external drive, the data on the internal hard drive may have already been corrupt and you have simply been backing-up corrupted data. This would be unfortunate and there would not be many ways to get around this issue. Nevertheless, data corruption is a fairly obvious issue and since you appear to have not noticed any data corruption to date hopefully none has occurred.