You should only remove the java1.4.2update2.pkg file if the system disallows you from installing the 1.4.2 java. If this is the case it will either say, already installed no update necessary or give a null error. Only in that case do you remove the receipt file which can be found in the OSX HDD -> Library -> Receipts folder. Receipts folder sample image. The system requires the receipts files so normally these files should never be touched.