Browser clear history can be done by running Opera always in "private mode"
Use the shortcut on you desktop (or make one if you've throwed it away..).
Right mous on the icon and go to the "target" fill out field.
Change it to:
"C:\Program Files\Opera\launcher.exe" --private
or
"C:\Program Files (x86)\Opera\launcher.exe" --private
Depending upon the location where the opera.exe is.
Click ok and it is done...
The moment you close the browser all history is gone automatically...
The (important) consequence.... is that after you reopen Opera it does not open the preferred pages... I think (did not test that as I do not want to loose my current pages..)