I don't know so this is a guess, it may of inserted a line into your autoexec.bat or win.ini or similar file that is run at startup, have a look through them to see if you can see a line inserted giving this setup option.
From windows click start run and type sysedit and the aforementioned files will pop up in a text editor.
Be very careful though, make sure you make copies of them first, just in case.