Chkdsk is hanging, C: is dirty, files are randomly corrupting

Part of what you've said is happening on a friend's machine, and I have two others that have boot issues which are very similar. XP SP3 on relatively recent (checked good using Ubuntu usb drive) hardware. Windows boot interrupts, chkdsk runs and then

Consistently for me,

"while it is repairing the unreadable security descriptors data stream, it gives the same output with the additional message:

Unable to read from attribute 128 of file 9.

and then chkdsk ends"

This friend has a few hundred gig of data to recover and I'd rather restore the OS and return the puter to her for backup vice buying an external hdd to do it with Ubuntu.

:4-dontkno any assistance would be appreciated.