Q:

I found a some bad sectors with chkdsk. Should I be worried?

Yesterday I found a corrupted file in my external usb drive.
Since I am using the drive quite often (I am running my vms over there) I decided to run
the chkdsk on it
This is the result 
488384000 KB of total space on disk.
351202364 KB in 1042390 file.
489920 KB in 81101 indexes.
    16 KB in damaged sectors.
1204584 KB in use.
65536 KB used from the registry.
135487116 KB available on disk.

therefore it has found 16KB of damaged sectors.
Now the file is recovered
Should I be worried about the HD and run chkdsk periodically from now on?

A:

If you find damaged sectors at all, it means the drive has already gone through its remap pool and has run out of blocks to transparently remap. That means your drive is dying. You should replace it now.
You should never see bad sectors from a normal OS utility, because the drive should be hiding them in the background.

A:

I would run chkdsk periodically to make sure that this doesn't degrade further, but a few damaged sectors here and there is normal and nothing to be particularly worried about. During normal operation, a hard disk will (transparently to the operating system) re-map any damaged areas to non-damaged areas, and report that in the SMART data.
Which brings me to the next point, that you may want to download and install (if you don't have already) a utility which will allow you to inspect the SMART data from the drive. I'm not too sure what's available in Windows to do so or if it'll work over a USB connection, but that will tell you if the drive is remapping large amounts of space or only a few odd blocks here and there. If it is remapping a lot of space, then you should consider replacing the drive as soon as reasonably possible to avoid the risk of data loss.
The drive can transparently remap only a given amount of data, and when it runs out, then data errors are going to start trickling through to the OS. Which is why you want to keep an eye on any damaged blocks count reported by the OS utilities. If that number increases by any significant degree, that is a good indication that the drive is about to fail.

