Could updating Win10 (from 1607 to 1703) delete your files?

[Scorpio187]

I've been on 1607 (Anniversary Update) until today when I finally received a message via update center that I can now update and move on to ver. 1703 (Creators Update).

Anyway, after it was finished installing I noticed something. Right before installing 1703, I had 46.4 GB free of 190 GB on C disk and 137 GB free of 273 GB on D disk. After updating it was 39.3 GB on C and 166 GB on D. I then had to restart my laptop - Bitdefender wouldn't launch - so after restarting my laptop I noticed that it shows 137 GB once again on disk D. However, disk C now shows 39.1 GB.

Where did those 7.3 GB go?

 

[Dahak]

Windows.old folder (keeps a backup of the previous os) and possibly some left over folders from the upgrade, usually hidden

Also for most antivirus you should remove them first and re-install them after as they tie in pretty low level to the os and sometimes can cause issues with the upgrade