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High-Tech Times Article 026

Fighting - & Winning - With Windows NT

Welcome back to the High-Tech Times. As Iíve mentioned many times, my articles reflect the problems that my clients bring to me. And this month, it appears that Microsoft has provided the largest battleground with its Windows NT products. Iíve had at least 15 calls from people who were simply unable to boot their NT systems!      So Iím going to provide one simple bit of info that might save your bacon if (when) you run into this type of problem.

If your Windows NT boot partition is too large or it is not the first partition on the hard disk, your computer may suddenly refuse to boot. Why are we seeing more of this problem today? Well, think about how much you would have had to spend just five years ago to buy the same 22 GB hard-drive that I paid $250 for this week....

Windows NTís NTFS disk format allows huge partitions. With a 512-byte cluster size, you can format a partition of 2 terabytes (TB). Thatís two trillion bytes: enough to hold over four million novels. The maximum 64KB cluster size allows 256TB, or well over half a billion books. But even though NT can address all of this huge space, the boot process starts with your BIOS (Basic Input/Output System), not Windows NT.

The BIOS locates the beginning of a partition by using three numbers: the Starting Side (or Head), the Starting Cylinder, and the Starting Sector. The end of a partition is identified by three similar numbers. Now, the Side value is 8 bits, and can range from 0 to 255 (256 numbers); the Cylinder is 10 bits, and can range from 0 to 1023 (1024 numbers); the Sector is 6 bits, and can range from 1 to 63 (63 numbers - note that zero is not a valid sector number.) This means the maximum address on the disk is Side 255, Cylinder 1023, Sector 63. The number of sectors is 256 X 1023 X 63, or almost 16.5 million sectors. Standard sectors are 512 bytes, so we have a size of 7.87GB.

Thatís the point: The BIOS cannot access anything beyond the first 7.87GB of the hard disk. If any critical boot data, such as the files NTLDR, NTDETECT, or BOOT.INI, get moved to a point more than 7.87GB from the start of the hard disk, your computer will not boot. Anything that moves one of the critical files may cause the problem; you may have copied the file from another partition, or you may have edited the file. But you will not be aware of any problem until the next time you boot.


Youíre vulnerable to this if the partition on which Windows NT is installed is larger than 7.87GB, or if this partition is not the first partition on the disk and the total of this partition and all of the partitions before it exceeds 7.87GB.

The first thing to do is to boot up your computer using a boot floppy. This is simply a floppy formatted on a Windows NT machine (that is vital), and containing copies of NTLDR, NTDETECT.COM and BOOT.INI. The BIOS accesses the floppy and finds the data it needs, then the floppy starts Windows NT, and everything runs fine. Of course, the next time you boot, the problem is back, but this gets the machine up and running so you can get your regular work done. Now you can schedule a time to fix it when you wonít disrupt production.

Now, to fix it. The problem is simply that some critical file or files lie beyond the part of the disk which the BIOS can access. The simplest handling is to use the BIOS to rewrite the file. Start with your Windows NT Setup Floppies and CD, and proceed as if you were installing a second Windows NT installation. When asked which folder to use, specify a new folder, not the one that the existing Windows NT is in. When asked if you want to check the hard-disks for errors, select ďyesĒ. Once this check is done, you can abort the new installation and Windows NT will boot up successfully.

Another way is to move the critical files back closer to the beginning

of the disk. This can be difficult because you really donít know where the files will be placed when you copy or move them. However, the odds are on your side if the partition lies mostly within the 7.87GB limit. Trial and error will do it.

The simplest prevention is to always have the boot partition as the first

partition on the hard disk, and ensure that it is less than 7.87GB. If this is not feasible, take steps to ensure the critical files will not be moved. If the partition is in NTFS format, set the access on those files so that only an administrator can access them, and if you are using a defragmenter such as DisKeeper or Norton, add the critical files to the defragmenterís exclusion list.

For those of you who can access Microsoftís TechNet, Iíve referenced Microsoft Knowledge Base Articles Q114841 and Q127134. As Windows 2000 comes closer, and we all try to load up final betas and release candidates, I think that this information may prove to be quite useful....

See you next month.