Found this on the web - hope it helps:
"TaskMon monitors your hard drives disk access patterns during program loads and logs the information to a hidden Windows directory called APPLOG. When you go to defrag your hard drive, Disk Defragmentor uses the information found in this directory to optimize your system by placing all the files that a specific program needs to load in the same area on the hard disk. This reduces the number of lengths the disk needs to seek, which account for a large chuck of load times for any application.
TaskMon collects data as you use applications and adapts to optimize the applications you run most frequently. Example: If you run Netscape more often than I.E. 4.0, Defrag will concentrate on optimizing Netscape program loading vs. I.E. Program loading. After you finish defragging the application (s) should open faster."
As for Scanreg, this creates backups of your registry so you can restore from a good back up if necessary (using the Scanreg /Restore command).