There are several indexing function in the windows OS and in MS Office, these are supposedly to help speed up searches by indexing your files and in the case of office your documents. Personally I think they are a waste of space.
I have long since disabled the Windows Indexing service, if you have a look at the properties of each partition of hard disk you will see something like Allow Indexing Service to index this disk, uncheck that option, see image.
MS Office used to have something like FastFind which I also disabled, that was a very long time ago and I haven't upgraded from Office 97 Small Business Edition, I simply didn't need the bells and whistles and if I ever do update it, then it will be something like OpenOffice.
So you will need to have a search on the windows Help and Support function (from the Windows Start button) or MS Office or Word Help to see how to disable any fastfind/indexing function.
P.S. you won't get this sort of help with any other AV (especially for unrelated issues) and avast by comparison is lighter on resources and highly configurable.