If you can't access the old drive where the archived
hands were saved then your only option is to email the sites as suggested above, but most sites can't email hands in the same format that PT4/HM3 need to be able to import them. If you play a site like Stars/FTP, Party or WPN you can email their support and ask for all your old hand histories and tourney histories/results.
pokerstars/FTP and other sites like
ignition/Bovada, and GG Poker (and Natural8) have menus in their software that allow you to download the 'Last X' number of hands/tournaments or number of weeks/months of hands to import for review.
For future reference, to prevent this from being an issue if it happens again, I would suggest you configure your PT/HM to archive the auto imported/processed hands to a sub-folder of a cloud hosting service such as Dropbox or Google Drive like I do:
Regards,
Fozzy71
Customer Support
Hold'em Manager