I think a way to test if a defrag utility is working or not is doing a common man test. Since fragmentation affects how files are stored on the hard disk, it impacts considerably on starting programs up. This is the moment when the needed files are not in memory nor cached.

You should measure how long does your PC takes to start up till a certain point (may be showing one splash screen of an antivirus, showing msn messenger log in window, etc)
Besides you can count how many seconds Ms Words (or OO Writer) takes since double click to first blink of the cursor(a that point the software should be almost loaded). This should be done on a fresh reset, if you already ran one the application it may be cached and alter the results.

After you have done the measures, perform a full defrag using the utility you like the most.

Restart and measure the times again. I think this work if you have a PC highly fragmented, and the difference should be notorious.

These are my 2 cents for your blog.

Thanks for support Open Source SW, and thanks for allow me to post in your blog.

You might want to contact the guys who write the program or post a message on their forums on Sourceforge.