I'm using series60 3rd version. In my pkg file, I copied a dll file to !:\sys\bin\. But when I installed the sis file on phone, I got "can not install, component is built-in" error, then exit.

I guess that it is because there is already a dll file in the phone with the same name. So I judge the condition in the pkg file like this:
IF NOT (exists("!:\sys\bin\dllname.dll"))
"dllname.dll"-"!:\sys\bin\dllname.dll"
ENDIF

also I tried
IF NOT (exists("dllname.dll"))
"dllname.dll"-"!:\sys\bin\dllname.dll"
ENDIF

But it still gets the same error message.