Windows 7: ChkDsk safety question

Hi,

Several years ago, my old XPh system began behaving erratically. I finally decided to run chkdsk on the C drive, which I did from the command line, with the Repair switch.

Chkdsk indeed found disk errors, and I watched in horror as it began disallocating sector after sector. A huge portion of the drive was being taken offline before my eyes, and there seemed no end in sight. I intuitively felt that the drive really wasn't in that bad a condition to warrant this kind of action, and considered that I either was losing valuable data or soon would be.



I took the panic response and aborted the scan, hoping for the best. And I was glad I did. A 180G drive had lost some 30G to the disallocation, but my system ran fine on the now-reduced-size drive. Years later, after I took that old drive out of service I put a partition manager on it, re-allocated that lost space, reformatted, and the drive is full-sized and perfect again.

Now here is my question. Why did ChkDsk act this way? I never trusted it after that. Only recently, when I transferred to my new system, did I begin to use ChkDsk again, and it's performed fine. But I haven't forgotten the time it almost wasted my system, so I'm concerned about safety.

Sorry, this was meant to go under Hardware and Devices. Could it possibly be moved there?

Thanks,
p.