I bought bitcoins then my hard drive crashed. I recovered the drive and have the intact folder with my wallet.dat file etc. but do not know how to get them back and use them. And no, I did not make a paper wallet with my private keys. Yikes!
If you have recovered the wallet.dat file, then you’re in the clear. First, before doing anything else, you should make a few more backups of the wallet.dat. Perhaps store them on USB drives which you keep in a safe under your control and / or in your bank.
Next, reinstall Bitcoin Core (I’m assuming you’re using Bitcoin Core as it’s the most popular wallet which uses wallet.dat files – if using something else, then you can reinstall that software).
Once Core is reinstalled, run it for a few minutes then close it. It will generate a data directory. Depending on your OS, this will be located in different places. Here’s how to access it:
You’ll note that a new, empty wallet.dat file has been created by your new Core, within the data directory. If you now paste your recovered backup wallet within the data directory (overwriting the new, empty wallet.dat) and then open Bitcoin Core, you should see your former restored. It may be necessary to allow Core to fully sync to see your full balance, so once you’ve restored your wallet just give it all the time it needs to sync up with the current blockchain height.
Hope that sorts everything out for you. Remember to create those initial backups, just in case something goes wrong with this process – and because it’s always best to have backups, as you’ve probably realised.