Did you Verify or Repair. If you Repaired then that's not good if Disk Repair could not repair. Since you don't have the Hardware Disk that came with the machine, you may have to purchase a repair utility like DiskWarrior or something similar.
You could try booting into the Lion Recovery HD and Repair Disk from there.
To boot into Lion Recovery HD:
Restart your Mac and hold down the Command key and the R key (Command-R), and keep holding them until the Apple icon appears, indicating that your Mac is starting up. After the Recovery HD is finished starting up, you should see a desktop with a Mac OS X menu bar and a "Mac OS X Utilities" application window. Note: If you see a login window or your own desktop and icons, it is possible that you didn't hold Command-R early enough. Restart and try again.