I've only experienced a dynastat operation once and it definitely slows to a crawl. If I remember correctly,
@Steve tries to read each questionable sector 2000 times or something. I would assume the time remaining estimate counter is useless during that operation. I don't think there's any way SR can predict what's about to happen. As
@Tazz said, manually jumping to different parts of the disk may be useful. I think you can notate position up to 4 decimal places, both when terminating a scan or starting a scan. So, hypothetically (these numbers don't relate to your example), if you stop at 23.2347 % on a partition, you could continue at 23.2346 % later so there's just a bit of overlap if you want to start from the same point. Definitely consider moving the data off the drive where you can. Hopefully the file allocation tables weren't scrambled.
It's possible that the drive is functional and the data got scrambled by a power failure or lockup or something. So, you might be able to get the data off, do a full format (which erases all data) on the drive, then do a SR level 4 to thoroughly exercise each sector. If it passes that, use a disk monitor program to check for reallocated sectors. If there are lots of those, toss the drive. If the drive is making unusual noise, toss the drive. If it passes SR level 4 and there aren't lots of reallocated sectors and it's not making strange noises, you could continue to use it for non critical purposes where backups exist. If it's Windows 7 and it's original equipment, it's getting pretty old, especially if it's a spinner and not an SSD.
Finally, if you can get all the data to read, and if you leave it in there (may not be the best plan) and if it's a spinner, do a defrag on it. If you put in a spinner to replace it, do a defrag on that once data is copied to the new one. If you put in an SSD, they don't need defragging. Windows 7 sometimes has problems knowing you've put in an SSD. There are procedures to check that it knows that. Turn the defrag system off for any SSD's. Also, if you have any other drives in the system, put temp files and swap files on those other drives to reduce wear on the SSD. If you only have the one drive, you don't have a choice on that.
I just thought of this at the end but you may wish to try it first. Assuming the PC can run on the drive, you could turn off the page file / swap file and also turn off hibernation. Then reboot. This will delete those huge files. Then see if SR can scan through the drive without kicking into dynastat. If so, one or both of those files could have been the problem. SR may still jam up if the sector data is unreadable. But, as
@Tazz alluded to, if nothing's there, it may not matter. A full format (not a quick format) will rewrite every sector with zeros I think. Of course, this also erases all data. You'll want to turn the page file / swap file back on and hibernation back on later once you've either recertified the old drive or installed the new drive.
May your bits be stable and your interfaces be fast.
Ron