Windows 7 - Bizarre issue with harddrive's CHS geometry

My PC's harddisk is a Samsung HD321KJ (32MB cache, 7200rpm, 320GB).

I was messing around with partitions today in a futile attempt to align my Windows system, and eventually just gave up and restored an image I had made just before.

In the process I noticed something totally weird...the drive itself suddenly reports a different CHS geometry. It used to be something like 38913, 255, 63 but now it reports 43009, 255, 57. Now all my partition software thinks track 0 is just 57 sectors long.

The total number of sectors on the HD remains the same, and there's no other ill effect so far. But...how the heck did this happen? Can I convince the drive to reset its reported CHS numbers? How?

I don't know the answer to your question, but I did have to go into the interwebs and expand my knowledge. Here are two interesting articles on the subject:
Cylinder-head-sector - Wikipedia, the free encyclopedia
Disk formatting - Wikipedia, the free encyclopedia

My take is that CHS geometry is a largely abandoned process that is ignored by most modern operating systems (pre-XP).

Are you running a dual boot with an old OS (DOS or similar) where this "low level format" is important? Is this condition causing an issue?

No, no issue at all. Not dualbooting either.

I ran a DOS-based diagnosis tool from Samsung called ESTool and it offered low-level format and other options to reset the drive's reported size to its native size. Oddly, the native size is 625142448 but it would only "reset" to 625142447, exactly one sector less.

However, I unexpectedly solved the issue by simply wiping the HD with a diskpart -> clean command and then restoring my latest system backup to a freshly created partition. Now the drive reports the old, proper CHS data again.

Totally weird, as I was convinced it was a problem with the drive's own firmware settings. But...chalking this one up to the God of Computing Glitches and marking it solved.

Thanks