When trying to update my outlook, I also had trouble
with .pst files not showing up in my searches when
searching my entire computer. I finally found them in
a roundabout way. Check for them using this path:
on your C drive (or whatever drive you work from)
\Documents and Settings\yourname or userid\Local
Settings\Application Data\Microsoft\Outlook
Make sure you have your explored set to show hidden files.
If they are not there, in Outlook, go into
Tools -> Options -> Mail Setup
Click the button for Data Files. This should bring up a
window which shows you the entire path, but it may get
cut off in this view. You can click the button to open
the folder, it will open it up in an explorer window and
you can view the entire path better from here.