Hi
I created a bitcoin wallet once to pay for a service from a site, but i never bought the service and kept the bitcoins. I also very shortly did some mining.
And i changed OS a few times since so i have no files what so ever form then.
So if i don't have a wallet.dat file i have lost that wallet for good ?
//Brian
You have no way to recover your wallet now since wallet.dat is the main and primary base of your wallet which you lost.
Next time take care of your wallet and i recommend you to use other online wallet services from blockchain or xapo or coinbase atleast if u have the private key you cannot loose your wallet in any way !