Why did XP decide my partition has NO file system?

[Angelfood MacSpade]

My ordeal started with a forced shutdown of XP (I have to do this on
occasion). CHKDSK started up to check my drive N: (the only partition
in a 180GB WD drive), finished quickly and found no errors. However
now XP (Disk Management) thinks my N: drive is empty and has NO file
system. It was formatted as NTFS and was (and is) about 50% full.

The really fascinating thing is that all my disk utilities like
PartitionMagic 8 and Active Partition Recovery do not see any errors
whatsoever - and see the file system as NTFS.

I can use an undelete utility to recover my data across my network,
format the drive and restore everything but it will take the entire
day. But is there something I can do within XP to convince it that the
drive has an NTFS file system??

One implicating factor might be that I recently changed this partition
to 64K file clusters from 4K (it's used primarily for video storage).
Although everything seemed fine for a day, could this file cluster
change have messed up XP somehow?

 

[Angelfood MacSpade]

It now looks like my hard drive is no longer useable. I have
reformatted in Disk Management - first using the quick format option.
All appeared fine until I rebooted and then once again XP decided the
drive had no file system. I then did a full format, copied my data
back, rebooted once and all looked fine. But after a 2nd reboot, the
drive is again without a file system. What a huge PITA.