CHKDSK not fixing corrupt partition

I have a 250GB HDD which I have split into two partitions (C and D), recently, my D drive was acting very slow so I decided to do a CHKDSK on startup. It took all day (literally) to the point where I had no option but to hard reset the system. It was checking files which I didn't want anymore at the time though, so after this I decided to move over the files which I wanted to my C drive, and simply do a full format of the D drive.

I just recently did a CHKDSK and it gets to about half way through the free clusters and then gets VERY slow and when its almost finished it'll just stop running. Additionally I'm get a SMART warning that my HDD is about to die, but I think its just that part of the D drive is corrupt, my C drive works flawlessly as it always has but as soon as I start messing with the D drive everything will slow down.

It was probably my fault for interrupting the CHKDSK but I had to turn it off at that point anyway.

I'm running CHKDSK again now in Windows (instead from startup) hopefully it'll complete but if not I'm completely lost. What can I do if it fails?

Ok everything's backed up. I'm 99% sure the CHKDSK was the cause of this. Everytime I try to do it (done it on startup, safe mode and within Windows) it always starts to slow to a near halt and the same part, until it freezes. I'm pretty sure there's nothing wrong with the drive physically as this only happened after the check and there's no loudness coming from the drive.

Using seatools just gets to about 15% then gives a FAIL, within it:

Fix All Fast - FAIL 13/06/2012 2:59:54 AM
SeaTools Test Code: A5DBC4CE

And says use seatools for DOS.

You should always use the bootable extended CD scan, however even if it repairs your HD to where Disk Check also confirms it's good now, I would not trust it again after what you've reported.

SeaTools for DOS | Seagate

Even though it was kinda me that did it?

In the future ask Google or here to see if you should interrupt something that's taking a long time. Some yes, some no.

I did, and decided to take the risk. It had already been running for well over 10 hours.

If I can get it back up and running then I'll hold onto it as long as possible and then just get an SSD, but if it fails again like this then I'll just replace it sooner.

For now I'd rather just get it fixed.

Ok did the startup disc and it failed on the long test. Anything else I can try? I read about 'zerofill', will that help?

I would not run a HD which fails HD diagnostics and Disk Check.

You can try to format it to quarantine the bad sectors but even if it works it will be at risk of imminent failure.