Backup fails when creating shadow copy

Since buying a new PC with pre-installed Home Premium I have been trying to
make a backup copy. Every attempt ends with the same failure. The system
event log contains "The file system structure on the disk is corrupt and
unusable. Please run the chkdsk utility on the volume OS_Install." I have
run chkdsk several times and it has never found any errors (it always finds
5 unindexed entries but I don't believe this is a problem). I have no
confidence in my PC vendor's software support, its latest "solution" has
been to reinstall Vista, which I am reluctant to do in view of the fact that
everything else works and I have had no problem in accessing my files. The
expanded view of the event is: -
- <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
- <System>
<Provider Name="Ntfs" />
<EventID Qualifiers="49156">55</EventID>
<Level>2</Level>
<Task>2</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2007-05-21T18:14:29.505Z" />
<EventRecordID>27431</EventRecordID>
<Channel>System</Channel>
<Computer>PSTEMESH</Computer>
<Security />
</System>
- <EventData>
<Data />
<Data>OS_Install</Data>
<Binary>0D0004000200300002000000370004C000000000020100C00000000000000000000000000000000089420300</Binary>
</EventData>
</Event>

Does the binary data give any clues as to the identity of the "corrupt
directory"?