Search Crawls creating folders with each file in root of c: drive

using SharePoint foundation 2013

when the search crawl runs overnight - it seems to be creating a folder for every new file it finds to add to the index?

I have 71 folders created by the sharepoint apppool account in teh root of my c: drive

I can't find any information about this behaviour or how to stop it!

any thoughts on that?

MrP