installation of MS Office 2007 in window xp professional

I am having window xp professional with window 2000 in my desktop ; i have downloaded trial version of office 2007 from microsoft;when i tried to install i am getting a msg;”window installer service cannot update one or more protected folders”; I have removed all passwordprotected files already; still i am getting the same msg;pl. let me know the solution for this

Pattabiraman a.v