fixing c stage 1 5 % ( 248589 of 427520 ) total 2 % eta 103.59.00

If you don't have to save the data, I say format the disk on the same machine. Then, theoretically, Win 10 shouldn't have a problem with it and it may well be a lot quicker.

Take backup of your data. After facing this problem my hard drive failed. You should also look at performing a short DST check if your system. Look it up on the internet on how to do it.

I went through this with 5 disks. 'Fixing EL\ Stage 1' - there appear to be four stages in this chkdsk but I didn't find that out at the time. 

Whenever it was running (fixing) it took between 1 hour and 2 - no matter what the estimate said. I think it's one of those funky system estimates i.e. based on a disk this size and the amount of work I'm doing - it's going to take 904 days!

But it doesn't take into account all the occupied space it isn't going to touch. And available disk space appeared to be another factor, not necessarily factored into the estimate. If there are Move operations going on, they may be inefficient when the available space is low.

I've never heard of anyone losing data, but it is disconcerting.

You have no other option besides to wait and let it complete. The more you interrupt it by restarting, the chances of data being damaged increase.

But how long will it take to complete. It shows 83 hours !!!

I never got to the bottom of this particular variant of Chkdsk. I took drives that were completely healthy and working out of my old machine and put them into a win 10 machine. I couldn't believe any fixing had to be done but I discovered that MBR drives were listed as CBT after the 'Fixing' - so it may not be fixing anything, it might just be doing a conversion. Definitely don't interrupt it, let it do it's thing and all will be well.