Upgraded Windows 7 to Windows 10, Window Search service no longer starts
Solution 1:
The problem is due to the fact that before the upgrade the search index was on a different drive. One that was no longer available after the upgrade.
As soon that I changed the value of HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\Gathering Manager\DefaultApplicationsPath to a path on the drive C: the Indexer started working perfectly. (There were other paths to fix, but the above is the one that would cause the service to fail).
Strangely enough, the path involved and the missing drive were not among the path returned by Process Monitor.
Solution 2:
After much research I finally was able to restore indexing in my Windows 10. The message I received was about error 3 mentioning that the system was not able to find the specified path.
Tried several "recipes" with no success and was almost performing a refresh install, then I found your comment about the index pointing to a non-existent drive. In my case, these keys were pointing to a "G:" drive:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\Gathering Manager G:\Windows_Index\Search\Data\Applications\ HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\TempPath G:\Windows_Index\Search\Data\Temp\usgthrsvc
First I used services.msc to disable the Windows Search Service.
Windows 10 Registry Editor does not allow editing of these keys. I downloaded and installed the free home edition of "Registrar Registry Manager" from
http://www.resplendence.com/main and was able to change the keys to the following values:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\Gathering Manager\DefaultApplicationsPath to value: C:\Windows_Index\Search\Data\Applications\
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\Gathering Manager\TempPath to value: C:\Windows_Index\Search\Data\Temp\usgthrsvc
Under services.msc I made the change for windows Search to start automatically (delayed start). It started normally as it should.