as far as i know there are two ways to recover one's btcm first: having the private key, second: getting the wallet.dat - right?
i don't have access to the private key, but i do have access to the hard drive, the wallet.dat was on (althought deleted, might be overwritten, might be not).
what ways do i have to
a) recover the wallet.dat
b) get access to my btc again?
That's right. If you manage to get your wallet.dat file back, you can recover your wallet.
You can try a recovery software like
Recuva or
EaseUS.