To remove the Menu Bar (the one with File/Edit/View and so on) open the 'opera6.ini' in your main Opera folder (C:\Program Files\Opera) and insert this line:
Show Menu=0
You can also edit the 'input.ini' file in the main Opera folder to have the option of showing the Menu bar by pressing the F10 key. Just add the lines below:
[Application]
F10 = Show popup menu,"Browser Menu Bar"
