Windows don't permits creation text file

[niobi]

Hi,
I've written a program in environment DELPHI 7. This file is inserted in a launcher that I've sent to my client; he has installed then the file.exe on its computer (SO: VISTA/7).
My procedure works leaning to a simple text.file, but it must be before created at root (usually, "C:\").
The host SO prevent my file.exe to create the text.file to work, with the error message "Unable to write c:\File.Txt".
This problem probably derives by the system of writing permissions in the host SO, but by choice, the client don't must modify this system manually for me.
How can I bypass the Windows protection?
- don't write on C: and where?;
- create a new sub-folder free of limit: in which folder?;
- vary one key in HKLM: which?;
- install a .bat file: and it have permissions?;
My installer creates an icon on the desktop to launch the .exe file: in the .pif file, can I insert switches to ask SO that the permissions the .exe file to create/write files on the disk?
I've read many posts, but no contains solution for my problem.
I hope I was clear.

[Reverend Jim]

You could use the values of the environment variables HOMEDRIVE and HOMEPATH to get the location of the user's home directory then create the file in a folder under that, perhaps in "Documents"