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#11
A simple websearch would have given you info quicker than complaining about someone suggesting to upgrade to Windows 10 and something causing the Windows.old to be deleted, which I doubt was caused by Microsoft.
Rebuild System Partition
The second way here we can put forward is to rebuild the system partition. If you don't want to pay a penny to do the lost partition recovery, try this method. Note that this requires you have the Windows installation disk. Now follow the instructions to begin.
Preparatory work:
Boot the computer using the Windows installation media for your running OS. Then on the first installation screen, press SHIFT+F10 to bring up the command prompt.
Now run the following commands at the command prompt.
Step 1:
bootrec /fixmbr
Step 2:
diskpart
select disk 0
list partition
select partition n (n is the Windows OS partition)
active
exit (exit diskpart)
Step 3:
bootrec /fixboot
Step 4:
bootrec /rebuildbcd