One way would be to set mIRC up how you want it as default, then make a backup copy of the entire mIRC folder somewhere.
Make a vbscript or a batch file (IMHO a VBScript is better because it runs invisibly) to delete the entire mircdir contents and copy the backed up folder back into it, and then finally run mirc.exe
Change the shortcut in the start menu|desktop to run that instead of mirc. Change the icon to mirc's icon :[/b])
That way, each time it's run, it is a clean copy set up exactly as you wanted.
