language problem

I’ve Windows 2000 in English, Office 2000 in English too… This is an IBM Thinkpad Laptop. It was pre-installed. This is the laptop of my boss.
When I open the Explorer windows, I ‘ve some menu in French and some menu in English. Very, very strange, I asked my Boss if he didn’t installed some program in french, he said me no !
Ok ! but what’s wrong, Please help me !