1321 The Installer has insufficient privileges to modify this file

I am sole administrator of my system running windows xp but when i try installing update for any applications that i have installed i get an error message saying "1321 The Installer has insufficient privileges to modify this file: filename"

I don't know what's wrong, i am not able to uninstall and reinstall any application as well. It says "access denied". I never had this issue earlier it all started suddenly.

Some recent changes in your system might have caused this issues. Either you have installed some third party application or some windows update recently. In both cases i will suggest you to do a system restore to a point when you were not facing any such issues.