Hi!

Recently, after a power surge, it developed a "bad block" (4kb marked as
bad),
but it still works correctly.
Q: What is a "bad block" in a hard drive?
Physical damage?

Usually, yes. It is not really possible to manufacture a truly "perfect"
hard disk even today. Onboard controllers have become smarter and with
automatic defect relocation schemes drives appear to be defect free deal, at
least in the onset. Over time, as the media inside wears down additional bad
spots can develop.

Advanced disk repair utilities (like the GRC tool, SpinRite, at
http://grc.com/) can sometimes convince the drive's electronics to replace
the bad spot with a good spare.

Sometimes these spots start to spread like wildfire and the drive is soon
rendered unreliable. Other times (much more common) the drive simply
develops a little defect for no readily apparent reason. I have a few like
this that have been running for years and no further defects or bad spots
have appeared.

I've also had at least one 2.1GB Western Digital that was almost totally bad
as per Scandisk yet it still managed to hang on long enough to copy all of
its data with only one lost file! That operation took all night with the
drive making bad "retry" sounds, but when I put in the replacement drive and
placed all the files back on it, the system and its OS were no worse for the
wear. I was amazed...that was the only time I've ever seen that happen.

Basically, keep an eye on your drive. Back up the contents and run a disk
utility every now and then. If the drive seems OK, don't let your guard
totally down...just continue to keep an eye on it and if you see things
start to get worse--get the data off immediately (hard disk drives don't
usually give out as many warnings as the WD unit above...) and get a new
drive.

Note: please don't give me TinyURL addresses.

I don't use that service, and have never tried it, but why not?

William