The following article is the first in a series that helps solve many of the common boot problems with hard drives. The article explains how to verify the drive functionality, determine the correct setup for the drive, and repair problems with the Master Boot Sector once the drive is verified to be functional. This information will help solve some very common problems encountered in a computer service department. This article is designed to work with a system that has a single drive with one bootable partition using a FAT 16 structure (all DOS and older Windows systems), and no drive overlay.
It is extremely important not to make or write any changes to data on the hard drive without first verifying the hard drive configuration. Therefore, the first priority when unable to access information on a hard drive is to verify all of the configuration information dealing with the suspect hard drive.
Partition Parameter Value or Equation Partition Status Bootable Starting Head 1 Starting Sector 1 Starting Cylinder 0 Partition Type Bigdos (drives greater than 30 MB), otherwise DOS 12 Ending Head Total Number of Heads -1 Ending Sector Sectors per Track displayed in Volume Boot Sector Ending Cylinder Number of Cylinders set in CMOS - 2 Total # of Sectors Number of Sectors displayed in Volume Boot Sector Start Absolute Sector Number of Sectors per Track in Volume Boot Sector Boot Signature 55AA
Step One: Make sure that Micro-Scope detects the hard drive
In Micro-Scope, System Configuration, Compare Settings - check to make sure that there is not an asterisk beside the number of hard drives detected value. If there is an asterisk, either the CMOS is set incorrectly, or there is an electronic problem (controller, cable, drive).
Step Two: Compare the BIOS parameters against the drive partition information.
In Micro-Scope, System Configuration, System Information - note the information displayed for the hard drive, specifically the parameters for the drive in question. Compare these parameters to the parameters in the MBR display under Micro-Scope, System Configuration, Partition Display using the following formula:
System Information Master Boot Record Cylinders Ending Cylinder + 2 Heads Ending Head + 1 Sectors Sectors Per Track
If the information does not match, either the partition information is corrupt, or the CMOS setup or controller BIOS setup (if one exists) is incorrect, or there is a problem communicating with the drive.
Step Three: Check the drive functionality
In Micro-Scope, Diagnostics, Fixed Disk Tests - check the information in the Fixed Disk Selected window. Make sure that the proper drive type, model, and native parameters are showing in this window. If any of the information is incorrect, there is an electronic problem. Check the cable, controller and drive, re-seating all connections, and repeat the above procedure. After correcting the electronic problem, perform a read test on the first 10 cylinders of the drive. If any errors occur, then this is the most likely cause of the drive failure. Perform a read of the entire drive to determine if the errors are electronic in nature, or physical in nature. Electronic problems will result in the errors displayed not always being the same type or in the same location on the drive. If the problem is electronic, replace the cable, controller, and finally drive electronics and repeat the read test until no errors occur. If the error is physical, use an INT 13 type editor (such as Norton Advanced Editor), to block the entire drive and write the information to a daisy chained drive set to the same parameters as the faulty drive.
The next step, after the drive passes the read test on the first 10 cylinders, is to check the original partition setup of the drive.
Step Four: Check for the physical location of the master boot sector and the volume boot sector.
In Micro-Scope, Utilities, Fixed Disk Editor - use the FIND feature to search the last two bytes of each cylinder for a boot signature (55 AA). The first location where a boot signature should be found would be at cylinder 0, head 0, sector 1 (the master boot sector). The second location where a boot signature should be found is at cylinder 0, head 1, sector 1 (the volume boot sector). It is also possible to use the FIND feature to locate the volume boot sector by searching for MSDOS (in DOS based systems) or MSWIN (in Windows95 systems).
If there is a duplicate copy of the master boot sector found before the location of the volume boot sector, then it is possible that a boot virus has infected the hard drive in the system. The Rebuild Master Boot feature of Micro-Scope will eliminate any boot sector virus. Be sure to boot the system to the Micro-Scope diskette and immediately do a cold reboot of the system after using the Rebuild Master Boot feature.
If the volume boot sector is found in a location other than cylinder 0, head 1, sector 1, count the actual number of sectors before the volume boot sector, and compare that value to the value for the sectors per track displayed in the partition table described in step 2. If the values match, the most likely cause of the system failure is an incorrect CMOS setup. In this case the CMOS needs to be reset to the values indicated by the partition table described in step 2, remembering to use the formula described in step 2 when doing so. If the values do not match, set the CMOS Sectors Per track to the number of sectors counted before the volume boot sector and continue to the next step.
Step Five: Check the partition tables to make sure they are correct
Reboot the system to Micro-Scope and go to System Configuration, Partition Tables. Check the information displayed in the master boot record to see if there is any obvious corruption (that is, excessively large numbers, all partitions non-bootable, etc.) If there is no obvious corruption in the master boot record, then perform step 2 again. If the information matches at this point, go to step 6. If the information does not match, then set the sectors per track in the Master Boot Record to the number of sectors per track currently set in CMOS, set the starting head to 1, starting sector to 1, and starting cylinder to 0, and write the information to the drive.
Step Six: Verify the Master Boot Sector information
Display the Volume Boot Sector and use the values for heads and sectors per track (on the right half of the screen) to perform step 2 again.
If the values match, then the volume boot sector is probably okay. If any values in the Master Boot Record do not match the table to the right, reset the values to match the values in the table, and write to the drive.
If the values still do not match, both the Master Boot Record and the Volume Boot Record are probably corrupt. At this point, e-mail Technical Support for help in this situation. Future articles will provide more insight into the repair procedure.
Step Seven: Check the FATs
Check to see if the first FAT starts on the sector just beyond he volume boot sector. Use the find feature in the Fixed Disk Editor to search for F8 FF FF in the first three bytes of each sector. The first occurrence should be on sector two of head one. Continue to search until the second FAT is found, indicated by the second occurrence of F8 FF FF. Note the location of the cylinder, head and sector of the second FAT.
Based on the start of the second FAT, and the start of the first FAT, calculate how many sectors are in the first FAT. If necessary, read each sector starting at the first sector of the first FAT, keeping a count of the sectors that have been read until F8 FF FF is seen in the upper left of the HEX display, which would indicate the start of the second FAT. After calculating the sectors per FAT, compare this value to the value in the volume boot sector. If the values match, the drive should be accessible through DOS at this point.
Step Eight: Attempt to access the drive
Boot to a DOS-bootable floppy diskette and attempt to access the drive. If the root directory and sub-directories on the hard drive are readable at this point, then attempt to boot to the drive. If the drive boots at this point, the problem has been corrected. If the drive is still not bootable, e-mail the Micro 2000 Technical Support department for help.
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Micro2000 is an industry leader in PC hardware diagnostics for Windows® computers through its award-winning MicroScope™ series and have been providing utilities to the marketplace for over 15 years. For more information please visit www.micro2000.co.uk
