Short version: You probably need Bitcoin Core (now 200 GB), and the file you're looking for is wallet.dat.
Make safe offline backups before doing anything else!
Long version: [overview] Recover Bitcoin from any old storage format.
Make safe offline backups before doing anything else!
Long version: [overview] Recover Bitcoin from any old storage format.
If the blockchain was 5Gb, then the coins you have got in the wallet will probably buy you a Lambo. 
Judging by his post history:Mine is : 1QCvEe6xU6Dsh83bxEaEsh8ftGnoqUvgoH
He's looking at at least 2BTC ($7000). And that brings me to the next point: Don't trust any PMs you receive!