fixing a corrupt .pst file

outlook2003 has suddenly crapped out after no problems for the past 1.5years - the program will not start for only one of the profiles on the computer, so I think it must be the .pst file. Won't start in safe mode either. Error messages are varied, but now it just chugs away and then quits with a 'not responding' message. I have read about scanpst as a repair tool, and have found it in Windows7, but now can't find the .pst files to direct it to check. Where are they?!

Thanks for reading and great site btw.

A simple search for "where are outlook 2003 files stored" found THIS.