Where's the Outlook PST file?

My new Dell Inspiron 1520, running Vista Home Premium crashed and will not reboot.  Tech support will not help me with this problem! :smileymad:  The system runs but will not go to the Windows desktop or programs, but I can get a command prompt and see directories and files. 

I need to find my Outlook PST fil which contains my most recent emails, the only data which was not backed up before the crash.  What folder is it most likely in for Outlook 2007?

Tech supports tells me I must wipe the system clean and start over, but after a week of installing software, I'm reluctant and not convinced the system cannot be fixed.  Any suggestions for doing that?

Thanks in advance.

MitchC