Try reading this general info about pst files here
http://support.microsoft.com/default.aspx/kb/829971
Make sure:
1. You are running the same version of Outlook from your old PC as on the
new one.
2. Logged on as an administrator
3. Open the pst file from within Outlook: File > Open > Open data file... >
browse for the file in question
4. If Outlook opens the file, good you are OK.
If OK:
1. To un-encrypt the files and save with no encryption (to save you this
headache in the future) Export the file as a pst without encryption.
2. File > Import and Export... > Export to a file > Personal Folder file
(.pst) > Choose the pst file in question > make sure to check the box
"Include subfolders" >
Browse for a destination folder and select "Allow duplicate items to be
created" (to prevent leaving something out - you can clean this up later) >
rename the file (if you don't want the generic name) and click OK > Finish
3. Now a dialog box will pop-up that allows you to change some settings such
as the file title/name and encryption choices. Your choice might be No
encryption.
4. Save your files.
Please post your results.