I recently backed up my blockchain to an external drive and restored my computer from Windows 10 to XP. Afterwards, I copied the blockchain back to my hard drive and downloaded a portable copy of Bitcoin Core and ran it. It said it had many hours to sync, and I left it overnight. When I came back, it had crashed with XP's message about it needing to close. I opened it again and it said that some part of the blockchain files were corrupt and started syncing from 2009. I restored my backup again and it only had 34 hours to catch up on.
Today I got up and the same error was displayed. But this time when I reopened it, it only has to catch up on 2 hours. If it works then that's great, but does anyone know what's happening?