If you can – as suggested – shut your computer down right now and attach the affected hard disk to another computer for the recovery process. It's imperative that you make as few changes as possible to your computer right now, as any data written to your hard disk might overwrite the deleted files and makes them unrecoverable. I've used Recuva in the past, and it worked quite well.
If you chose to delete the files, you'll need a third-party program to undelete them. Start an Explorer with administrative privileges (press Win + E and run explorer) and go to the deleted users' profile (usually C:\Users\USERNAME).
If you chose to keep the files, you can still access them with any administrator account. When you delete a user account, Windows asks you whether you want to delete or keep the files.