In your February post, you indicated the laptop was a 2005 Gateway MX6441. When you say "6-month old" laptop, do you mean you've only had it 6 months, and perhaps you bought it used? If you did purchase it new, was your warranty 90 days or a full year?
It is unusual for a hard drive to fail after only 6 months, but I have seen it happen.
In the February post, I provided a link to Gateway's hard drive diagnostic utility. Did you download and run that diagnostic to test the drive for errors? If so, did it report errors? If you didn't run it, please do that at your earliest convenience. You should be able to confirm/deny hard drive problems.
Replacing the hard drive in this laptop doesn't appear difficult at all. See this Gateway link
that explains (with pictures) how to replace the drive.
You said you ran Chkdsk on C:\ and D:\. In the February post, we discussed backing up your data and doing a system recovery. Did you do that? If so, and the drive is again giving you the imminent failure alert, then I'd say the drive is failing and you should immediately backup your data (if you didn't already).
Because your system is a Gateway, you need to review the links I provided about creating a Recovery Disk and also this Gateway link
that explains how to perform a system recovery to a new/blank hard drive.
As I stated in the February post, it is vitally important that you create a Recovery disk before your hard drive fails, because Gateway stores the OS files on a partition of the hard drive.