I'm sorry you've lost all your stuff, it's happened to me in the past too
On the question of recovery, it depends.
When files are "overwritten" not all the blocks may be hit.
It also depends upon how many times they have been "overwritten".
If you are using a Mac, Prosoft have a program called Data Rescue, which I've used with "some success" in the past.
I see they have a PC version, but I've never used it.http://www.prosofteng.com/products/
I work for the largest storage company in the world, so backup and retention is my thing.
We have a rule of "3 copies, with one of them offsite" in the industry.
I'm not suggesting you need the level of protection that I use, but I don't want to lose my photos, music or documents, so I follow that mantra at home too
All my Macs have shares to a QNAP NAS which runs on my network 24/7.
It has 8x 2TB Enterprise drives running in RAID 6.
This automatically backs up to the Cloud using CrashPlan+, direct from the NAS.
I also have a Dell Server that has a hardware RAID controller and external enclosure with 8x 1.5TB in RAID 5, used once a month as an Rsync backup from the QNAP.
This way, worst case, I still have a copy on CrashPlan's servers in the Cloud that I can recover if absolutely necessary.
CrashPlan+ is very cheap, has unlimited storage (I currently store 2.1TB) for $50 a year and more importantly, they don't throttle you after a certain data size.