Thanks for the links--I'm currently using EaseUS and while it has recovered a lost partition and many gigabytes of files, not all of them are actually "recovered", but just remnants of them (perhaps this is why the deep scan has recovered 1300G, while the hardrive is only 500G).
At least some photos are showing up, and it will be a tedious process of going through all the individual files to see if they are "pre-viewable" which would mean they are recoverable. I also tried DiskDrill which helped me save an overwritten doc. before, but most files were unrecoverable due to being overwritten; Recuva also had the same results.
As it is not my PC but a colleague's, I will see how important the data is for him, and the next step is to send the HD to a professional who has the right equipment for this job.