I am running WinXP Pro SP3. Defraggler works fine on the admin account. However, on my limited account, Defraggler displays "Processing aborted due to: Access is denied" when I click on Defraggler's Defrag button. The reason I installed Defraggler was to defrag on the limited account and shut down the PC at the end of the day (I only use the admin account for installing software due to security reasons).
I am using Defraggle version 184.108.40.206. I experienced the same problem with the regular installer and the portable version. I following the documented instructions for creating the portable.dat file in the same directory as the executable.
When I run "df.exe C:" from the limited account, I see in the cmd window "Access Denied. Administrator permissions are needed to use the selected options. Use an administrator command prompt to complete these tasks." When I try to run as administrator Defraggler.exe, Windows says it cannot access it!
In the short term, I plan to switch to using JKDefrag (http://www.kessels.com/JkDefrag/), which allows defrag of files that are accessible by the limited account, but has no PC shutdown option. In the long term, I hope Piriform will improve Defraggler so that it will support limited accounts. Many people want the portable version for use on their PC at work, where they are on a limited account.
By the way, the standard Defraggler installer did not install a desktop shortcut or a Start Menu item in the limited account. Also, why not put the portable.dat file in the ZIP distribution for the portable version?