Outlook .pst file down to 0 bytes and unable to restore system

When I switched on my computer this morning I was confronted with a light
blue screen and the computer started to perform chkdsk.

When I opened Outlook 2002 it told me that my mailbox.pst was not a Personal
Folder File.
On inspection I saw that it was now down to the size of 0 bytes in my
settings folder, compared to an older backup version which is nearly 150MB.
I ran scanpst but it said that my mailbox.pst was not large enough to
contain any data, which at 0 bytes isn't an unexpected response.
My other .pst files seem OK, together with their respective backup files.
The backup for my main one [mailbox.pst] is over two weeks old so I would be
missing emails of the interim period.

When I tried a System Restore within XP it came back to me saying it
couldn't.
I have over 95GB of free space on my harddrive and had the slider to the max
for system restore allottable space.
I tried numerous restore points - all with no success.

Checking the System Event viewer in Computer Management doesn't give me any
clues really.
There are no recent 'sr' instances but a few 'Unable to start a DCOM server
ones'.

There was a 'ntfs' event Error at 2.47 pm yesterday that said that 'The file
system structure on the disk is corrupt and unusabel. Please run the chkdsk
utility on the volume C'

I was messing about with IIS 5.1 yesterday afternoon (around 5pm) and just
browsing using IE6 at about 9.45pm when I shutdown.

Any help gratefully received

Sean

_______________________________________________
Windows XP Professional with all the latest SPs and patches.
Athlon XP 2.2 (1.8 Ghz)
512 MB RAM
120 GB HD all one volume