Based on the file names, I am guessing that you are running on Windows. If so, get FileMon from SysInternals (http://www.sysinternals.org/) and run it, that should tell you what is using those files.
From personal experience, I ran into this situation in two ways: 1) my anti-virus software was scanning the files 2) a corporate-required "virus" that does software inventory had the files open.
Er axlly it's on a unix based server. Although I can access the file system from windows.