Still short on time but one to keep.
Windows10 has completely fragmented the hard drives on both the machines I've upgraded. One of the reasons I usually don't upgrade.
My recommendation.
Defrag before you upgrade
Defrag after you upgrade.
I also noticed that after the upgrade Windows had managed to mess up areas that can't be defragmented online. So in the end I used two defragmentation tools. Both free.
My suggested approach.
Defragment with
Defraggler before you upgrade. It's quite good for general defragmentation. Make sure you don't check the "Move unused files to the end of the drive". That stops it fully consolidating.
Here's the tricky part.
After the upgrade...
Defragment again with Defraggler until it can't defragment any more. You'll see it leaves fragments behind
Defragment again with
Puran defrag, clicking Only on the Boot time defrag with the C drive selected.
Select Reboot Defrag Reboot.
It will reboot the machine, defragment with a black text based interface and then reboot back into Windows.
When it's completed and reboots again, re run puran defrag using the Defrag button with the C drive selected.
Just a point to note here. In Additional Options don't select fill gaps or free some space. Do select Optimise directories and also PIOZR
When Puran has completed for the second time run Defraggler again.
That's cleaned up my VM. My netbook, which was so slow it was almost unusable, is in the process now. It's going to take a few days as the hard drive is very slow and the netbook cpu is not very quick (deliberate choice).
All of this is going to take quite a while, possibly even a day or two, but, however, you should have a machine which is performing about as well as it can given it was an upgrade and not a clean install.