A helpful tip from the ESRI Support Services Blog: 

We have all been there…you kick off a large process, and while waiting for it to complete, you start to wonder, “Is this process still running?”

Many geoprocessing tools are memory intensive, and depending on the size of the input datasets and the type of computation, it can take hours to run.

If you find yourself staring at the computer screen after your 10th cup of coffee and still wondering, “Is this thing still working!?”, there is a quick and easy way to tell.  Read more...