The following function will attempt to remove the read only flag on a file, you will need the function in this article (http://www.howtodothings.com/ViewArticle.aspx?Article=755).
function RemoveReadOnly(const FileName: string): Boolean;
begin
(* Assume Success *)
Result := True;
(* Make sure the file is read only before
we try and change the attributes *)
if (IsReadOnly(FileName)) then
begin
SetFileAttributes(PChar(FileName), FILE_ATTRIBUTE_NORMAL);
Result := not IsReadOnly(FileName);
end;
end;