Everyone has been there. You sit at your computer, desperate to get on with some work, but the PC is busy. Something's clearly using up lots of processing capacity or hard disk activity, because everything's running very slowly. So where are the culprits?
The normal course of action at this point is to load up Task Manager, or Process Monitor, or Resource Monitor. But they're not really designed for anyone except techies such as my self and my highly sophisticated team, and the results can be hard to interpret. Which is why I recommend a very simple tool called What's My Computer Doing for people such as yourselves.
The program is a 0.5 MB download that needs no installation. Just click on the enormous Download button to get it. When you run it, it tells you which programs are running, and whether they're using hard disk, processor, or both. Click on one of the entries and you can see more about the program, as well as sending it directly to VirusTotal for a scan if you're suspicious.
If you're not technically minded but you want to keep your PC running at its best, What's My Computer Doing is the program you need.