Locate the PST file on your old drive
Select File | Import and Export... from the menu in Outlook.
Select Import from another program or file. Click Next.
Highlight Personal Folder File (PST). Click Next again.
Now use the Browse button to select the backup copy of the PST file you want to recover from your old drive.
Make sure Replace duplicates with items imported is selected.
Finish the import process with Finish.