I foolishly upgraded to 10 from 7HP OA 64bit at the begining of the month and all appeared fine except for occasional unexplained desktop background changes until yesterday.
Suddenly the start menu dissappeared and search did not work.
On line info suggested this was common and suggested a fix using powershell
Fix failed
With no start menu I struggled to access restore or similar options
Found access to restore and selected most recent retore failed and no boot
Several Blue Screens later and promises to repair etc non of the restore points were viable. I had no boot
Following on screen suggestions I tried Reset ...... Failed due to Cortana problem ???? said Boot device inacessable etc etc
Eventually found access to safemode and managed to boot and restore worked on third attempt.
Roll back to win 7 failed due to all folders in win old being empty or deleted by MS before the month was up
Still no solution to start menu or search cannot rollback and cannot download an ISO as Gateway/acer product key will not verify
No Cortana because it is now not available for english english and no edge as I cannot find it and no other apps
I have a broken system but I have managed to restore some functionality although it is very slow.
Some one suggested a conflict with Avast so have removed Avast and Defender is running

Advice will be gratefully received