Hi, Thanks for your responses. Yes, I've found the .pst file, but when I start outlook, it says that it is the outlook.ost file which needs to be repaired with the scanpst.exe programme.
However, when I log onto my pc, it logs me in automatically as administrator, there are no other accounts set up, beyond default which doesn't appear to have anything in it. I am therefore assuming I have been using the administrator account for everything and that this hidden outlook.ost file must be somwhere within the 'administrator' account, but unfortunately I cannot find it. (I will try to reveal the hidden files as suggested, to see if this reveals anything).
Incidentally, on my laptop (running vista) i can find my outlook.ost file as this has been set up with an independent user account, I just can't find the file on the pc which is set up as administrator account only.
Thanks for your help so far.
Will