Check5 is a monitoring tool which displays changes to the contents of a specified folder (and all its subfolders) in real time.
If you want to find out what's happening on your system drive, for instance, you might click Folder Monitor > Add Folder to Monitor, and choose drive C (or whatever it might be). And then, as you launch anything which creates, amends or deletes files - Firefox, say - so those actions will be displayed in the main File List Grid.
Viewing changes across the whole drive can generate a little too much information, of course, but if you're getting lost in the details then you can always specify the folders which interest you, like \Program Files, \Users, or whatever combination you need.
An Event Logging menu allows you to decide exactly what you want to record, too: files created, edited, renamed or deleted.
And if this isn't enough, Check5 also includes various batch file management tools which you can apply to the logged events. So if, say, you've recorded 500 new files being created in a particular folder, then the program can rename all of those according to the rules you specify, in a single operation.
That's the theory, anyway. In practice we found this aspect of the program to be horribly impractical, but it's there if you're interested. And even if you're not, it doesn't really matter - the file monitoring feature justifies installing Check5, all on its own.