How Does ATIH (11) number the disks when reporting errors

I am trying to do a back up of a 2 TB drive that shows as unformatted but actually (i hope) contains nearly 2 TB of data, before attempting any file recovery software.
The following drives are connected to the computer as per Disk Management:

C: 80 GB System drive - Disk Management = D1
D: 2 TB drive - shows as unformatted, 100% free space = D2
E: 2TB BU drive = D0 (newly formatted NTFS)

When I start up ATIH it shows Analyzing partition... in the lower left hand corner. The green bars get about half way across the box and then pause. After a short wait the error message comes up:

"Failed to read from the sector: #,###,###,### of the hard disk 3"

Sometimes the first number or two is negative, as in -1,853,991,296.

For some numbers clicking retry moves on to a different number, sometimes the next in the sequence and sometimes skipping hundreds or thousands. I have tried this several times and there are a few sectors that keep coming up on succesive tries, while others appear only once in a while.

So here's the question(s):
How does ATIH number the drives? Clearly it does not use the sequence that Disk Management uses. Is disk 3 = drive E: or does it start with DO and call it 1 so that disk 3 would be equivalent to D:?

Secondly, what is the meaning of a negative sector number?

And finally, I hesitate to run chkdsk on the drive I am trying to recover before getting a sector copy, but wondering if the drive that is reporting errors above is indeed that drive what would happen if I choose ignore all? Or am I better letting it go thru the entire sequence and hit retry a couple times before hitting ignore? What happens to the sectors that are ignored while doing the partition analysis in a sector by sector copy? Will it try again in the copy process to read the sectors that were ignored at startup, because if it does then i might as well ignore all at start up and wait until the copy process starts to retry a few times for each problem sector. And what kind of a back up will i end up with if there are dozens or even hundreds of unreadable sectors?

This is on a Dell VOSTRO 200 w 3 GB memory running XP Home. SP03
Thanks for any and all insight into the process.
ed