To Paul, I’ll point out that inside the [screen saver] settings for this is a “Do not defrag if last run was less than X hours ago” dropdown, and when it’s done, or if it decides not to run, it will switch over to the proper ’saver of your choice. I will also argue that the wear and tear from reading fragments repeatedly would outweigh that from straightening them out, while simultaneously expressing my feeling that this program really seems to enjoy moving files around. With the default settings, it seems to move certain large files, like the Google Earth cache and Street Atlas database, about every time it runs. So maybe the “Defragment only, do not optimize (’-a 2′ in the ‘commandline options’ box)” option would be best for frequent runs.

Another good one is Ultradefrag, which can run ‘at next boot’ or ‘at every boot’, which allows it to handle system files, and I have just now discovered has recently released version 2.