2.4 is the VERSION (Revision) of your BIOS. 2.1 Refers to the SLIC table that is inside a BIOS and is used to Activ*te Win 7 and Vista.
If it's an AMI BIOS just make a request in this thread with all the necessary info and a link to the BIOS that you want Modified with SLIC 2.1 for Win 7.