Soulseek should be your first port of call. It's a modern P2P client (think DC++) which has an incredible amount of music (as well as other things!) shared. One neat thing is that you can browse users' collections, so if you search for an album or song and find it, there's a good chance that user might have a lot more music you're interested (including stuff you didn't even know you wanted). Every now and then you'll come across locked shares where people are looking to trade, but that's pretty unusual (I've only come across it when looking for relatively rare or obscure releases).
For anime stuff specifically, try Nyaa.si. There's a bunch of clones, so make sure you go to the .si
one specifically. It's a public tracker, so your mileage may vary with how well-seeded things are, but large collections and recent releases tend to be okay. You may see links to blogs where an uploader has direct downloads for things, which can be super helpful if the torrent is dead.
(also, I should have led with this, but: sorry your hard drive died, that fuckin' blows. Best of luck in rebuilding your library, and hope you can find some new favorites in the process)