if csssrv.exe is running, we might have a way to figure out what is using it
Download
Process explorer and run it as admin (it comes from Microsoft so its safe) - its like an over poiwered version of task manager, i use it mainly for finding ram problems, but it has other uses.
clicking on the header for processes changes the view. default is tree view but it can also be sorted into alphabetical as well.. Tree view shows what it is running under, many programs run under services.
now find csssrv.exe in the list of running services, and right click on it, choose properties.
the Image tab will show its current location and details of ownership
Try looking on the threads page, it might give a clue as to what is using it
the other tabs are less useful for your current purpose.
This page shows what all the colours and headings mean, link at bottom of it shows how to use it to find problems. You can right click exe files and run an av scan from within the program.
alas, it doesn't show sys files.
it shows way too much info for this question but its always fun to see under the hood. It can show how much ram or hdd or cpu every process is using.