Dear PCR
I think I found the answer. The process must be something like this:
1- Dbl-Clk event
2- Mouse pointer changes
3- A "form" is loaded into memory. ("Form" is the special page (window) which is supposed to appear)
4- "Menu Bar" is loaded into memory. (RAM)
5- "Tool Bar" is loaded into memory.
6- "Status Bar" is loaded into memory.
7- "Web Contents" column is loaded into memory.
8- The "Form" appears with "Menu Br" & "Status Br" & "Web Contents column".
9- System asks for a list of related files and folders (Not subfolders). (I think asks it from registry)
10- The list of files and folders appear.

The most time consuming steps are 3&4&5&6&7, but step 3&4&5&6 (I think) are only done the first time I want to open a window. On next tries, these steps are ignored. So the problem occurs only on first try. Two other reasons may also cause the problem. First: The list of file and folders (Not subfolders) is too large. Second: Another program is occupying CPU and RAM.

There are several solutions for this:
1- Turn off "Tool Bar", "Status Bar" and "Web Contents".
2- Not to let the list get too large.
3- Exit other programs before clicking on "My Documents"
4- Use a faster CPU and a higher RAM.

Finally, I think that the best choice is not to do anything and let the problem occure on first open. On next tries it won't take place.

Javad