That's the Message Store Manager tool - you'll find it's home page with help file and training video here:
http://www.ciscounitytools.com/App_MSM.htm
Yes, you can stop it just fine - someone must have set it up to run on a schedule on your box (it wouldn't do that on it's own) - if you want to use it, be sure to snag the lattest version of the above site - we've fixed a few bugs in it since the release of 4.0(3).
