Thanks very much for Your reply LUII, but:
1. I cannot use Linux; I'm in a working environment where many programs I need to use are only for MS Windows, so ...
2. Admin rights: the PC is used by a girl at the office, so I don't give her admin rights in order to avoid unwanted installations
3. Defrag + using = problem: I know it, but I will schedule defragging only once a week or a month, during lunch hour, so when the PC is not used ...
So finally the questions remains: I need to execute Defraggler with user rights in MS Windows XP SP3 in unattended mode (with scheduling);
Is it possible or not?
Thanks in advance to everybody.